diff --git a/src/base/abci/abc.c b/src/base/abci/abc.c
index eee4432b1..8d95d60b4 100644
--- a/src/base/abci/abc.c
+++ b/src/base/abci/abc.c
@@ -61033,7 +61033,7 @@ int Abc_CommandAbc9eSLIM( Abc_Frame_t * pAbc, int argc, char ** argv ) {
           }
           params.synthesis_approach = atoi(argv[globalUtilOptind]);
           globalUtilOptind++;
-          if ( params.synthesis_approach < 0 ||  params.synthesis_approach > 2)
+          if ( params.synthesis_approach < 0 ||  params.synthesis_approach > 3)
               goto usage;
           break;
         case 'I':
@@ -61249,7 +61249,7 @@ int Abc_CommandAbc9elSLIM( Abc_Frame_t * pAbc, int argc, char ** argv ) {
           }
           params.synthesis_approach = atoi(argv[globalUtilOptind]);
           globalUtilOptind++;
-          if ( params.synthesis_approach < 0 ||  params.synthesis_approach > 2)
+          if ( params.synthesis_approach < 0 ||  params.synthesis_approach > 3)
               goto usage;
           break;
         case 'I':
diff --git a/src/opt/eslim/delayEngine.cpp b/src/opt/eslim/delayEngine.cpp
index 0604a242a..5e92566cf 100644
--- a/src/opt/eslim/delayEngine.cpp
+++ b/src/opt/eslim/delayEngine.cpp
@@ -83,11 +83,13 @@ namespace eSLIM {
     } 
     int replacement_size = synth.getSizeFromActivationVars(last_model);
     int replacement_delay = synth.getDelayFromDelayVariables(last_model);
-    assert (replacement_delay > 0);
-    std::vector<bool> model = synth.reduceDelay(replacement_size, replacement_delay - 1);
-    if (model.size() > 0) {
-      replacement_size = synth.getSizeFromActivationVars(model);
-      std::swap(last_model, model);
+    assert (replacement_delay > 0 || replacement_size == 0);
+    if (replacement_delay > 0) { // a constant circuit has already optimal depth
+      std::vector<bool> model = synth.reduceDelay(replacement_size, replacement_delay - 1);
+      if (model.size() > 0) {
+        replacement_size = synth.getSizeFromActivationVars(model);
+        std::swap(last_model, model);
+      }
     }
     return synth.getReplacement(last_model, replacement_size);
   }
diff --git a/src/opt/eslim/windowMan.tpp b/src/opt/eslim/windowMan.tpp
index d09b264ab..c540988a3 100644
--- a/src/opt/eslim/windowMan.tpp
+++ b/src/opt/eslim/windowMan.tpp
@@ -126,7 +126,7 @@ namespace eSLIM {
       std::cout << "PThreads not available, minimize random window.\n";
       std::uniform_int_distribution<> udist(0, windows.size() - 1);
       int wid = udist(rng);
-      eSLIM_Man<SynthesisEngine, SelectionStrategy>::applyeSLIM(windows[wid], cfg, wlogs[wid])
+      eSLIM_Man<SynthesisEngine, SelectionStrategy>::applyeSLIM(windows[wid], cfg, wlogs[wid]);
     #endif
   }