diff --git a/Changes b/Changes
index 2b0bb2d6f..ef975dbac 100644
--- a/Changes
+++ b/Changes
@@ -28,6 +28,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 ****  Fix disable iff in assertions. Closes #1404. [Peter Monsson]
 
+****  Fix huge case statement performance. Closes #1644. [Julien Margetts]
+
 
 * Verilator 4.024 2019-12-08
 
diff --git a/src/V3Case.cpp b/src/V3Case.cpp
index a9189621c..43ec3ec39 100644
--- a/src/V3Case.cpp
+++ b/src/V3Case.cpp
@@ -210,7 +210,12 @@ private:
                 return false;
             }
         }
-        if (m_caseItems <= 3) return false;  // Not worth simplifying
+        if (m_caseItems <= 3
+            // Avoid e.g. priority expanders from going crazy in expansion
+            || (m_caseWidth >= 8 && (m_caseItems <= (m_caseWidth + 1)))) {
+            return false;  // Not worth simplifying
+        }
+
         // Convert valueItem from AstCaseItem* to the expression
         // Not done earlier, as we may now have a NULL because it's just a ";" NOP branch
         for (uint32_t i=0; i<(1UL<<m_caseWidth); ++i) {