diff --git a/src/Convert/MultiplePacked.hs b/src/Convert/MultiplePacked.hs
index f328b6b..5a38a44 100644
--- a/src/Convert/MultiplePacked.hs
+++ b/src/Convert/MultiplePacked.hs
@@ -27,7 +27,7 @@ module Convert.MultiplePacked (convert) where
 
 import Control.Monad.State
 import Data.Tuple (swap)
-import Data.Maybe (isJust, fromJust)
+import Data.Maybe (isJust)
 import qualified Data.Map.Strict as Map
 
 import Convert.Traverse
@@ -118,7 +118,10 @@ traverseLHSM :: LHS -> State Info LHS
 traverseLHSM lhs = do
     let expr = lhsToExpr lhs
     expr' <- traverseExprM expr
-    return $ fromJust $ exprToLHS expr'
+    case exprToLHS expr' of
+        Just lhs' -> return lhs'
+        Nothing -> error $ "multi-packed conversion created non-LHS from "
+            ++ (show expr) ++ " to " ++ (show expr')
 
 traverseExpr :: Info -> Expr -> Expr
 traverseExpr typeMap =
@@ -220,46 +223,45 @@ traverseExpr typeMap =
                 range' = (simplify base, simplify len)
         rewriteExpr (orig @ (Range (Bit expr idxInner) NonIndexed rangeOuter)) =
             if isJust maybeDims && expr == rewriteExpr expr
-                then endianCondExpr rangeOuter
-                        (rewriteExpr $ Range exprOuter IndexedMinus range)
-                        (rewriteExpr $ Range exprOuter IndexedPlus  range)
+                then rewriteExpr $ Range exprOuter IndexedMinus range
                 else orig
             where
                 maybeDims = dims expr
                 exprOuter = Bit expr idxInner
-                base = fst rangeOuter
+                baseDec = fst rangeOuter
+                baseInc = BinOp Sub (BinOp Add baseDec len) (Number "1")
+                base = endianCondExpr rangeOuter baseDec baseInc
                 len = rangeSize rangeOuter
                 range = (base, len)
         rewriteExpr (orig @ (Range (Bit expr idxInner) modeOuter rangeOuter)) =
             if isJust maybeDims && expr == rewriteExpr expr
-                then endianCondExpr dimOuter
-                        (Range expr' modeDec range')
-                        (Range expr' modeInc range')
+                then Range expr' modeOuter range'
                 else orig
             where
                 maybeDims = dims expr
                 Just (dimInner, dimOuter, expr') = maybeDims
                 idxInner' = orientIdx dimInner idxInner
-                (modeDec, modeInc) =
-                    case modeOuter of
-                        IndexedPlus  -> (IndexedPlus , IndexedMinus)
-                        IndexedMinus -> (IndexedMinus, IndexedPlus )
-                        NonIndexed   -> error "invariant violated"
                 (baseOuter, lenOuter) = rangeOuter
                 baseOuter' = orientIdx dimOuter baseOuter
                 start = BinOp Mul idxInner' (rangeSize dimOuter)
-                base = simplify $ BinOp Add start baseOuter'
+                baseDec = BinOp Add start baseOuter'
+                baseInc = case modeOuter of
+                    IndexedPlus  -> BinOp Add (BinOp Sub baseDec len) one
+                    IndexedMinus -> BinOp Sub (BinOp Add baseDec len) one
+                    NonIndexed   -> error "invariant violated"
+                base = endianCondExpr dimOuter baseDec baseInc
                 len = lenOuter
                 range' = (base, len)
+                one = Number "1"
         rewriteExpr (orig @ (Range expr NonIndexed range)) =
             if isJust maybeDims && expr == rewriteExpr expr
-                then endianCondExpr range
-                        (rewriteExpr $ Range expr IndexedMinus range')
-                        (rewriteExpr $ Range expr IndexedPlus  range')
+                then rewriteExpr $ Range expr IndexedMinus range'
                 else orig
             where
                 maybeDims = dims expr
-                base = fst range
+                baseDec = fst range
+                baseInc = BinOp Sub (BinOp Add baseDec len) (Number "1")
+                base = endianCondExpr range baseDec baseInc
                 len = rangeSize range
                 range' = (base, len)
         rewriteExpr (orig @ (Range expr mode range)) =
diff --git a/src/Convert/Struct.hs b/src/Convert/Struct.hs
index 6621e30..d92e31f 100644
--- a/src/Convert/Struct.hs
+++ b/src/Convert/Struct.hs
@@ -250,11 +250,13 @@ convertAsgn structs types (lhs, expr) =
         -- converting LHSs by looking at the innermost types first
         convertLHS :: LHS -> (Type, LHS)
         convertLHS l =
-            (t, l')
+            case exprToLHS e' of
+                Just l' -> (t, l')
+                Nothing -> error $ "struct conversion created non-LHS from "
+                    ++ (show e) ++ " to " ++ (show e')
             where
                 e = lhsToExpr l
                 (t, e') = convertSubExpr e
-                Just l' = exprToLHS e'
 
         specialTag = ':'
         defaultKey = specialTag : "default"
@@ -395,13 +397,12 @@ convertAsgn structs types (lhs, expr) =
                 maybeFields = getFields subExprType
                 Just (structTf, fields) = maybeFields
                 (fieldType, bounds, dims) = lookupFieldInfo structTf fields x
+                base = fst bounds
                 len = rangeSize bounds
                 [dim] = dims
                 undotted = if null dims || rangeSize dim == Number "1"
                     then Bit e' (fst bounds)
-                    else endianCondExpr dim
-                        (Range e' IndexedMinus (fst bounds, len))
-                        (Range e' IndexedPlus  (snd bounds, len))
+                    else Range e' IndexedMinus (base, len)
         convertSubExpr (Range (Dot e x) NonIndexed rOuter) =
             if maybeFields == Nothing
                 then (Implicit Unspecified [], orig')
@@ -438,12 +439,14 @@ convertAsgn structs types (lhs, expr) =
                 [dim] = dims
                 baseLeft  = BinOp Sub (fst bounds) $ BinOp Sub (fst dim) baseO
                 baseRight = BinOp Add (snd bounds) $ BinOp Sub (snd dim) baseO
-                undotted = endianCondExpr dim
-                    (Range e' mode      (baseLeft , lenO))
-                    (Range e' otherMode (baseRight, lenO))
-                otherMode = if mode == IndexedPlus
-                    then IndexedMinus
-                    else IndexedPlus
+                baseDec = baseLeft
+                baseInc = case mode of
+                    IndexedPlus  -> BinOp Add (BinOp Sub baseRight lenO) one
+                    IndexedMinus -> BinOp Sub (BinOp Add baseRight lenO) one
+                    NonIndexed   -> error "invariant violated"
+                base = endianCondExpr dim baseDec baseInc
+                undotted = Range e' mode (base, lenO)
+                one = Number "1"
         convertSubExpr (Range e mode r) =
             (t', Range e' mode r)
             where
diff --git a/test/basic/struct_part_select_param.sv b/test/basic/struct_part_select_param.sv
new file mode 100644
index 0000000..8c0c259
--- /dev/null
+++ b/test/basic/struct_part_select_param.sv
@@ -0,0 +1,101 @@
+module Example;
+    // The test is equivalent to the struct_part_select test, except that all of
+    // the dimensions and indices have been replaced with parameters. This
+    // ensures sv2v can generate reasonable output even when nothing can be
+    // simplified down at the time of conversion.
+    parameter ONE = 1;
+    parameter TWO = 2;
+    parameter THREE = 3;
+    parameter FOUR = 4;
+    parameter FIVE = 5;
+    parameter SIX = 6;
+    parameter SEVEN = 7;
+    parameter EIGHT = 8;
+    parameter NINE = 9;
+    parameter TEN = 10;
+
+    typedef struct packed {
+        logic [TEN:FOUR] a;
+        logic [ONE:THREE] bx;
+        logic [THREE:ONE] by;
+        logic [THREE:FOUR][FIVE:SEVEN] cw;
+        logic [FOUR:THREE][FIVE:SEVEN] cx;
+        logic [THREE:FOUR][SEVEN:FIVE] cy;
+        logic [FOUR:THREE][SEVEN:FIVE] cz;
+    } T;
+    T t;
+    initial begin
+        $monitor("%2d %b %b %b %b %b %b %b %b %b %b %b %b %b %b %b %b", $time,
+            t, t.a, t.bx, t.by,
+            t.cw, t.cw[THREE], t.cw[FOUR],
+            t.cx, t.cx[THREE], t.cx[FOUR],
+            t.cy, t.cy[THREE], t.cy[FOUR],
+            t.cz, t.cz[THREE], t.cz[FOUR]
+            );
+
+        #1 t.a = 1;
+        #1 t.a[FIVE+:TWO] = '1;
+        #1 t.a[EIGHT-:THREE] = '1;
+        #1 t.a[TEN] = 1;
+        #1 t.a[SEVEN] = 0;
+
+        #1 t.bx[ONE+:ONE] = 1;
+        #1 t.bx[ONE:TWO] = 1;
+        #1 t.bx[THREE] = 0;
+        #1 t.bx[THREE-:TWO] = 1;
+        #1 t.bx[TWO] = 0;
+
+        #1 t.by[ONE+:ONE] = 1;
+        #1 t.by[TWO:ONE] = 1;
+        #1 t.by[THREE] = 0;
+        #1 t.by[THREE-:TWO] = 1;
+        #1 t.by[TWO] = 0;
+
+        #1 t.cw[THREE][SIX+:ONE] = 1;
+        #1 t.cw[THREE][SEVEN-:TWO] = 1;
+        #1 t.cw[THREE][FIVE+:TWO] = 0;
+        #1 t.cw[THREE][SIX:SEVEN] = 2'b10;
+        #1 t.cw[THREE][SIX:SEVEN] = 2'b01;
+        #1 t.cw[THREE:FOUR] = '1;
+        #1 t.cw[FOUR][FIVE] = 0;
+        #1 t.cw[FOUR][SIX:SEVEN] = 0;
+        #1 t.cw[THREE+:TWO] = 6'b010011;
+        #1 t.cw[FOUR-:TWO] = 6'b101011;
+
+        #1 t.cx[THREE][SIX+:ONE] = 1;
+        #1 t.cx[THREE][SEVEN-:TWO] = 1;
+        #1 t.cx[THREE][FIVE+:TWO] = 0;
+        #1 t.cx[THREE][SIX:SEVEN] = 2'b10;
+        #1 t.cx[THREE][SIX:SEVEN] = 2'b01;
+        #1 t.cx[FOUR:THREE] = '1;
+        #1 t.cx[FOUR][FIVE] = 0;
+        #1 t.cx[FOUR][SIX:SEVEN] = 0;
+        #1 t.cx[THREE+:TWO] = 6'b010011;
+        #1 t.cx[FOUR-:TWO] = 6'b101011;
+
+        #1 t.cy[THREE][SIX+:ONE] = 1;
+        #1 t.cy[THREE][SEVEN-:TWO] = 1;
+        #1 t.cy[THREE][FIVE+:TWO] = 0;
+        #1 t.cy[THREE][SEVEN:SIX] = 2'b10;
+        #1 t.cy[THREE][SEVEN:SIX] = 2'b01;
+        #1 t.cy[THREE:FOUR] = '1;
+        #1 t.cy[FOUR][FIVE] = 0;
+        #1 t.cy[FOUR][SEVEN:SIX] = 0;
+        #1 t.cy[THREE+:TWO] = 6'b010011;
+        #1 t.cy[FOUR-:TWO] = 6'b101011;
+
+        #1 t.cz[THREE][SIX+:ONE] = 1;
+        #1 t.cz[THREE][SEVEN-:TWO] = 1;
+        #1 t.cz[THREE][FIVE+:TWO] = 0;
+        #1 t.cz[THREE][SEVEN:SIX] = 2'b10;
+        #1 t.cz[THREE][SEVEN:SIX] = 2'b01;
+        #1 t.cz[FOUR:THREE] = '1;
+        #1 t.cz[FOUR][FIVE] = 0;
+        #1 t.cz[FOUR][SEVEN:SIX] = 0;
+        #1 t.cz[THREE+:TWO] = 6'b010011;
+        #1 t.cz[FOUR-:TWO] = 6'b101011;
+
+    end
+endmodule
+module top;
+endmodule
diff --git a/test/basic/struct_part_select_param.v b/test/basic/struct_part_select_param.v
new file mode 100644
index 0000000..6beeb9c
--- /dev/null
+++ b/test/basic/struct_part_select_param.v
@@ -0,0 +1,3 @@
+// The reference output for this test should match that of the
+// struct_part_select test.
+`include "struct_part_select.v"