diff --git a/mypyc/lib-rt/pythonsupport.c b/mypyc/lib-rt/pythonsupport.c
index 5c4df660863b..c2dda4f95ad2 100644
--- a/mypyc/lib-rt/pythonsupport.c
+++ b/mypyc/lib-rt/pythonsupport.c
@@ -5,6 +5,8 @@
 
 #include "pythonsupport.h"
 
+#if CPY_3_12_FEATURES
+
 // Slow path of CPyLong_AsSsize_tAndOverflow (non-inlined)
 Py_ssize_t
 CPyLong_AsSsize_tAndOverflow_(PyObject *vv, int *overflow)
@@ -50,3 +52,55 @@ CPyLong_AsSsize_tAndOverflow_(PyObject *vv, int *overflow)
   exit:
     return res;
 }
+
+#else
+
+// Slow path of CPyLong_AsSsize_tAndOverflow (non-inlined, Python 3.11 and earlier)
+Py_ssize_t
+CPyLong_AsSsize_tAndOverflow_(PyObject *vv, int *overflow)
+{
+    /* This version by Tim Peters */
+    PyLongObject *v = (PyLongObject *)vv;
+    size_t x, prev;
+    Py_ssize_t res;
+    Py_ssize_t i;
+    int sign;
+
+    *overflow = 0;
+
+    res = -1;
+    i = Py_SIZE(v);
+
+    sign = 1;
+    x = 0;
+    if (i < 0) {
+        sign = -1;
+        i = -(i);
+    }
+    while (--i >= 0) {
+        prev = x;
+        x = (x << PyLong_SHIFT) + CPY_LONG_DIGIT(v, i);
+        if ((x >> PyLong_SHIFT) != prev) {
+            *overflow = sign;
+            goto exit;
+        }
+    }
+    /* Haven't lost any bits, but casting to long requires extra
+     * care (see comment above).
+     */
+    if (x <= (size_t)CPY_TAGGED_MAX) {
+        res = (Py_ssize_t)x * sign;
+    }
+    else if (sign < 0 && x == CPY_TAGGED_ABS_MIN) {
+        res = CPY_TAGGED_MIN;
+    }
+    else {
+        *overflow = sign;
+        /* res is already set to -1 */
+    }
+  exit:
+    return res;
+}
+
+
+#endif
diff --git a/mypyc/lib-rt/pythonsupport.h b/mypyc/lib-rt/pythonsupport.h
index b11270a5d08b..85f9ec64ac90 100644
--- a/mypyc/lib-rt/pythonsupport.h
+++ b/mypyc/lib-rt/pythonsupport.h
@@ -129,11 +129,11 @@ init_subclass(PyTypeObject *type, PyObject *kwds)
     return 0;
 }
 
-#if CPY_3_12_FEATURES
-
 Py_ssize_t
 CPyLong_AsSsize_tAndOverflow_(PyObject *vv, int *overflow);
 
+#if CPY_3_12_FEATURES
+
 static inline Py_ssize_t
 CPyLong_AsSsize_tAndOverflow(PyObject *vv, int *overflow)
 {
@@ -161,7 +161,6 @@ CPyLong_AsSsize_tAndOverflow(PyObject *vv, int *overflow)
         res = CPyLong_AsSsize_tAndOverflow_(vv, &overflow_local);
         *overflow = overflow_local;
     }
-  exit:
     return res;
 }
 
@@ -183,10 +182,8 @@ CPyLong_AsSsize_tAndOverflow(PyObject *vv, int *overflow)
 {
     /* This version by Tim Peters */
     PyLongObject *v = (PyLongObject *)vv;
-    size_t x, prev;
     Py_ssize_t res;
     Py_ssize_t i;
-    int sign;
 
     *overflow = 0;
 
@@ -200,35 +197,12 @@ CPyLong_AsSsize_tAndOverflow(PyObject *vv, int *overflow)
     } else if (i == -1) {
         res = -(sdigit)CPY_LONG_DIGIT(v, 0);
     } else {
-        sign = 1;
-        x = 0;
-        if (i < 0) {
-            sign = -1;
-            i = -(i);
-        }
-        while (--i >= 0) {
-            prev = x;
-            x = (x << PyLong_SHIFT) + CPY_LONG_DIGIT(v, i);
-            if ((x >> PyLong_SHIFT) != prev) {
-                *overflow = sign;
-                goto exit;
-            }
-        }
-        /* Haven't lost any bits, but casting to long requires extra
-         * care (see comment above).
-         */
-        if (x <= (size_t)CPY_TAGGED_MAX) {
-            res = (Py_ssize_t)x * sign;
-        }
-        else if (sign < 0 && x == CPY_TAGGED_ABS_MIN) {
-            res = CPY_TAGGED_MIN;
-        }
-        else {
-            *overflow = sign;
-            /* res is already set to -1 */
-        }
+        // Slow path is moved to a non-inline helper function to
+        // limit size of generated code
+        int overflow_local;
+        res = CPyLong_AsSsize_tAndOverflow_(vv, &overflow_local);
+        *overflow = overflow_local;
     }
-  exit:
     return res;
 }