diff --git a/CMakeLists.txt b/CMakeLists.txt
index 27e805a..f55220b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -25,6 +25,7 @@ add_executable(fzc
 	src/compiler/utils/fzl_linked.c
 	src/compiler/utils/fzl_options.c
 	src/compiler/utils/fzl_ctable.c
+	src/compiler/checkers/fzl_loop_check.c
 	src/compiler/main.c)
 
 # Virtual machine
diff --git a/src/compiler/checkers/fzl_loop_check.c b/src/compiler/checkers/fzl_loop_check.c
new file mode 100644
index 0000000..8958292
--- /dev/null
+++ b/src/compiler/checkers/fzl_loop_check.c
@@ -0,0 +1,60 @@
+#include <common/fzl_opcodes.h>
+#include <common/fzl_types.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/fzl_walker.h>
+#include <compiler/utils/fzl_const_pool.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+// Check for infinite loop
+bool is_infinite_loop(fzl_walker_t *walker, size_t start_ip, size_t end_ip)
+{
+  if (!walker)
+    return false;
+
+  end_ip = (end_ip >= walker->op_count) ? (walker->op_count - 1) : end_ip;
+
+  // Can we determine an init block?
+  size_t maybe_init_start = start_ip + 1;
+  size_t maybe_init_end   = start_ip + 6;
+  fzl_const_t *declared   = NULL;
+  for (size_t i = maybe_init_start; i <= maybe_init_end; i++)
+  {
+    if (walker->ops[i] != FZL_OPCODE_STORE)
+      continue;
+
+    declared = &walker->consts->array[walker->ops[i - 1]];
+    break;
+  }
+
+  if (declared)
+  {
+    fzl_sym_t sym;
+    bool found = false;
+    for (ssize_t i = walker->sym_top - 1; i >= 0; i--)
+      if ((found = fzl_symt_get(walker->syms[i],
+                                (char *)declared->as.string.chars, &sym)))
+        break;
+
+    if (!found)
+      return false; // suspicious
+
+    if (sym.type >= FZL_TYPE_INT8)
+    {
+    }
+  }
+
+  // At least has jump outside
+  for (size_t i = start_ip; i <= end_ip; i++)
+  {
+    if (walker->ops[i] != FZL_OPCODE_JMP)
+      continue;
+
+    size_t jump_ip = walker->ops[++i];
+    if (jump_ip >= end_ip)
+      return false;
+  }
+
+  return true;
+}
diff --git a/src/compiler/fzl_walker.c b/src/compiler/fzl_walker.c
index bc269b5..ee6aa64 100644
--- a/src/compiler/fzl_walker.c
+++ b/src/compiler/fzl_walker.c
@@ -14,6 +14,8 @@
 #include <stdlib.h>
 #include <string.h>
 
+extern bool is_infinite_loop(fzl_walker_t *walker, size_t ls, size_t le);
+
 char *null_name = "<null>";
 char wlast_err[256];
 
@@ -271,6 +273,16 @@ fzl_walk_res_t walk(fzl_walker_t *walker, fzl_node_t *node)
         push_word(walker, start_ip);
         push_op(walker, FZL_OPCODE_RM_ENVTABLE);
 
+        bool is_infinite =
+            is_infinite_loop(walker, start_ip, walker->op_count - 2);
+        if (is_infinite)
+        {
+          snprintf(wlast_err, sizeof(wlast_err),
+                   "'%s': infinite loop detected at %ld:%ld",
+                   node->token->filename, node->token->ln, node->token->cn);
+          return (fzl_walk_res_t){.error = true, .error_msg = wlast_err};
+        }
+
         for (size_t i = walker->sym_top - 1; i > newctx->initial_env_lvl; i--)
           fzl_freesymt(walker->syms[--walker->sym_top]);