diff --git a/frontends/ast/simplify.cc b/frontends/ast/simplify.cc
index 5a9707976..6ab369817 100644
--- a/frontends/ast/simplify.cc
+++ b/frontends/ast/simplify.cc
@@ -4370,35 +4370,9 @@ AstNode *AstNode::eval_const_function(AstNode *fcall)
 	size_t argidx = 0;
 	for (auto child : children)
 	{
-		if (child->type == AST_WIRE)
-		{
-			while (child->simplify(true, false, false, 1, -1, false, true)) { }
-			if (!child->range_valid)
-				log_file_error(child->filename, child->location.first_line, "Can't determine size of variable %s\n%s:%d.%d-%d.%d: ... called from here.\n",
-						child->str.c_str(), fcall->filename.c_str(), fcall->location.first_line, fcall->location.first_column, fcall->location.last_line, fcall->location.last_column);
-			variables[child->str].val = RTLIL::Const(RTLIL::State::Sx, abs(child->range_left - child->range_right)+1);
-			variables[child->str].offset = min(child->range_left, child->range_right);
-			variables[child->str].is_signed = child->is_signed;
-			if (child->is_input && argidx < fcall->children.size()) {
-				int width = variables[child->str].val.bits.size();
-				auto* arg_node = fcall->children.at(argidx++);
-				if (arg_node->type == AST_CONSTANT) {
-					variables[child->str].val = arg_node->bitsAsConst(width);
-				} else {
-					log_assert(arg_node->type == AST_REALVALUE);
-					variables[child->str].val = arg_node->realAsConst(width);
-				}
-			}
-			backup_scope[child->str] = current_scope[child->str];
-			current_scope[child->str] = child;
-			continue;
-		}
-
 		block->children.push_back(child->clone());
 	}
 
-	log_assert(variables.count(str) != 0);
-
 	while (!block->children.empty())
 	{
 		AstNode *stmt = block->children.front();
@@ -4410,6 +4384,35 @@ AstNode *AstNode::eval_const_function(AstNode *fcall)
 		stmt->dumpAst(NULL, "stmt> ");
 #endif
 
+		if (stmt->type == AST_WIRE)
+		{
+			while (stmt->simplify(true, false, false, 1, -1, false, true)) { }
+			if (!stmt->range_valid)
+				log_file_error(stmt->filename, stmt->location.first_line, "Can't determine size of variable %s\n%s:%d.%d-%d.%d: ... called from here.\n",
+						stmt->str.c_str(), fcall->filename.c_str(), fcall->location.first_line, fcall->location.first_column, fcall->location.last_line, fcall->location.last_column);
+			variables[stmt->str].val = RTLIL::Const(RTLIL::State::Sx, abs(stmt->range_left - stmt->range_right)+1);
+			variables[stmt->str].offset = min(stmt->range_left, stmt->range_right);
+			variables[stmt->str].is_signed = stmt->is_signed;
+			if (stmt->is_input && argidx < fcall->children.size()) {
+				int width = variables[stmt->str].val.bits.size();
+				auto* arg_node = fcall->children.at(argidx++);
+				if (arg_node->type == AST_CONSTANT) {
+					variables[stmt->str].val = arg_node->bitsAsConst(width);
+				} else {
+					log_assert(arg_node->type == AST_REALVALUE);
+					variables[stmt->str].val = arg_node->realAsConst(width);
+				}
+			}
+			if (!backup_scope.count(stmt->str))
+				backup_scope[stmt->str] = current_scope[stmt->str];
+			current_scope[stmt->str] = stmt;
+
+			block->children.erase(block->children.begin());
+			continue;
+		}
+
+		log_assert(variables.count(str) != 0);
+
 		if (stmt->type == AST_ASSIGN_EQ)
 		{
 			if (stmt->children.at(0)->type == AST_IDENTIFIER && stmt->children.at(0)->children.size() != 0 &&
diff --git a/tests/various/const_func_block_var.v b/tests/various/const_func_block_var.v
new file mode 100644
index 000000000..98e83aa5b
--- /dev/null
+++ b/tests/various/const_func_block_var.v
@@ -0,0 +1,23 @@
+module top(out);
+	function integer operation;
+		input integer num;
+		begin
+			operation = 0;
+			begin : op_i
+				integer i;
+				for (i = 0; i < 2; i = i + 1)
+				begin : op_j
+					integer j;
+					for (j = i; j < i * 2; j = j + 1)
+						num = num + 1;
+				end
+				num = num * 2;
+			end
+			operation = num;
+		end
+	endfunction
+
+	localparam res = operation(4);
+	output wire [31:0] out;
+	assign out = res;
+endmodule
diff --git a/tests/various/const_func_block_var.ys b/tests/various/const_func_block_var.ys
new file mode 100644
index 000000000..7c2e85c64
--- /dev/null
+++ b/tests/various/const_func_block_var.ys
@@ -0,0 +1 @@
+read_verilog const_func_block_var.v