diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index 101619c8c..66f22e113 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -1708,25 +1708,27 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 				body_ast->children.size() == 1 && body_ast->children.at(0)->type == AST_GENBLOCK)
 			body_ast = body_ast->children.at(0);
 
-		if (init_ast->type != AST_ASSIGN_EQ)
-			log_file_error(filename, location.first_line, "Unsupported 1st expression of generate for-loop!\n");
-		if (next_ast->type != AST_ASSIGN_EQ)
-			log_file_error(filename, location.first_line, "Unsupported 3rd expression of generate for-loop!\n");
-
+		const char* loop_type_str = "procedural";
+		const char* var_type_str = "register";
+		AstNodeType var_type = AST_WIRE;
 		if (type == AST_GENFOR) {
-			if (init_ast->children[0]->id2ast == NULL || init_ast->children[0]->id2ast->type != AST_GENVAR)
-				log_file_error(filename, location.first_line, "Left hand side of 1st expression of generate for-loop is not a gen var!\n");
-			if (next_ast->children[0]->id2ast == NULL || next_ast->children[0]->id2ast->type != AST_GENVAR)
-				log_file_error(filename, location.first_line, "Left hand side of 3rd expression of generate for-loop is not a gen var!\n");
-		} else {
-			if (init_ast->children[0]->id2ast == NULL || init_ast->children[0]->id2ast->type != AST_WIRE)
-				log_file_error(filename, location.first_line, "Left hand side of 1st expression of generate for-loop is not a register!\n");
-			if (next_ast->children[0]->id2ast == NULL || next_ast->children[0]->id2ast->type != AST_WIRE)
-				log_file_error(filename, location.first_line, "Left hand side of 3rd expression of generate for-loop is not a register!\n");
+			loop_type_str = "generate";
+			var_type_str = "genvar";
+			var_type = AST_GENVAR;
 		}
 
+		if (init_ast->type != AST_ASSIGN_EQ)
+			log_file_error(filename, location.first_line, "Unsupported 1st expression of %s for-loop!\n", loop_type_str);
+		if (next_ast->type != AST_ASSIGN_EQ)
+			log_file_error(filename, location.first_line, "Unsupported 3rd expression of %s for-loop!\n", loop_type_str);
+
+		if (init_ast->children[0]->id2ast == NULL || init_ast->children[0]->id2ast->type != var_type)
+			log_file_error(filename, location.first_line, "Left hand side of 1st expression of %s for-loop is not a %s!\n", loop_type_str, var_type_str);
+		if (next_ast->children[0]->id2ast == NULL || next_ast->children[0]->id2ast->type != var_type)
+			log_file_error(filename, location.first_line, "Left hand side of 3rd expression of %s for-loop is not a %s!\n", loop_type_str, var_type_str);
+
 		if (init_ast->children[0]->id2ast != next_ast->children[0]->id2ast)
-			log_file_error(filename, location.first_line, "Incompatible left-hand sides in 1st and 3rd expression of generate for-loop!\n");
+			log_file_error(filename, location.first_line, "Incompatible left-hand sides in 1st and 3rd expression of %s for-loop!\n", loop_type_str);
 
 		// eval 1st expression
 		AstNode *varbuf = init_ast->children[1]->clone();
@@ -1738,7 +1740,7 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 		}
 
 		if (varbuf->type != AST_CONSTANT)
-			log_file_error(filename, location.first_line, "Right hand side of 1st expression of generate for-loop is not constant!\n");
+			log_file_error(filename, location.first_line, "Right hand side of 1st expression of %s for-loop is not constant!\n", loop_type_str);
 
 		auto resolved = current_scope.at(init_ast->children[0]->str);
 		if (resolved->range_valid) {
@@ -1779,7 +1781,7 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 			}
 
 			if (buf->type != AST_CONSTANT)
-				log_file_error(filename, location.first_line, "2nd expression of generate for-loop is not constant!\n");
+				log_file_error(filename, location.first_line, "2nd expression of %s for-loop is not constant!\n", loop_type_str);
 
 			if (buf->integer == 0) {
 				delete buf;
@@ -1825,7 +1827,7 @@ bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage,
 			}
 
 			if (buf->type != AST_CONSTANT)
-				log_file_error(filename, location.first_line, "Right hand side of 3rd expression of generate for-loop is not constant (%s)!\n", type2str(buf->type).c_str());
+				log_file_error(filename, location.first_line, "Right hand side of 3rd expression of %s for-loop is not constant (%s)!\n", loop_type_str, type2str(buf->type).c_str());
 
 			delete varbuf->children[0];
 			varbuf->children[0] = buf;