diff --git a/frontends/ast/ast.h b/frontends/ast/ast.h
index 08f91c9c3..89f7e6e4f 100644
--- a/frontends/ast/ast.h
+++ b/frontends/ast/ast.h
@@ -214,6 +214,8 @@ namespace AST
 			MEM2REG_FL_SET_ASYNC = 0x00000800,
 			MEM2REG_FL_EQ2       = 0x00001000,
 			MEM2REG_FL_CMPLX_LHS = 0x00002000,
+			MEM2REG_FL_CONST_LHS = 0x00004000,
+			MEM2REG_FL_VAR_LHS   = 0x00008000,
 
 			/* proc flags */
 			MEM2REG_FL_EQ1       = 0x01000000,
diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index 46013544b..589c683f8 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -113,6 +113,9 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 				if (memflags & AstNode::MEM2REG_FL_CMPLX_LHS)
 					goto verbose_activate;
 
+				if ((memflags & AstNode::MEM2REG_FL_CONST_LHS) && !(memflags & AstNode::MEM2REG_FL_VAR_LHS))
+					goto verbose_activate;
+
 				// log("Note: Not replacing memory %s with list of registers (flags=0x%08lx).\n", mem->str.c_str(), long(memflags));
 				continue;
 
@@ -2936,6 +2939,14 @@ void AstNode::mem2reg_as_needed_pass1(dict<AstNode*, pool<std::string>> &mem2reg
 				proc_flags[mem] |= AstNode::MEM2REG_FL_EQ1;
 			}
 
+			// remember if this is a constant index or not
+			if (children[0]->children.size() && children[0]->children[0]->type == AST_RANGE && children[0]->children[0]->children.size()) {
+				if (children[0]->children[0]->children[0]->type == AST_CONSTANT)
+					mem2reg_candidates[mem] |= AstNode::MEM2REG_FL_CONST_LHS;
+				else
+					mem2reg_candidates[mem] |= AstNode::MEM2REG_FL_VAR_LHS;
+			}
+
 			// remember where this is
 			if (flags & MEM2REG_FL_INIT) {
 				if (!(mem2reg_candidates[mem] & AstNode::MEM2REG_FL_SET_INIT))