diff --git a/src/include/lean/lean.h b/src/include/lean/lean.h
index f21d36c60d..69ca8df7d4 100644
--- a/src/include/lean/lean.h
+++ b/src/include/lean/lean.h
@@ -2664,15 +2664,19 @@ static inline size_t lean_isize_mul(size_t a1, size_t a2) {
 static inline size_t lean_isize_div(size_t a1, size_t a2) {
     ptrdiff_t lhs = (ptrdiff_t)a1;
     ptrdiff_t rhs = (ptrdiff_t)a2;
-
-    return (size_t)(rhs == 0 ? 0 : lhs / rhs);
+    if (rhs == 0) return 0;
+    // Check for overflow: PTRDIFF_MIN / -1 would trap on x86 idiv
+    if (lhs == PTRDIFF_MIN && rhs == -1) return (size_t)PTRDIFF_MIN;
+    return (size_t)(lhs / rhs);
 }
 
 static inline size_t lean_isize_mod(size_t a1, size_t a2) {
     ptrdiff_t lhs = (ptrdiff_t)a1;
     ptrdiff_t rhs = (ptrdiff_t)a2;
-
-    return (size_t)(rhs == 0 ? lhs : lhs % rhs);
+    if (rhs == 0) return (size_t)lhs;
+    // Check for overflow: PTRDIFF_MIN / -1 would trap on x86 idiv
+    if (lhs == PTRDIFF_MIN && rhs == -1) return 0;
+    return (size_t)(lhs % rhs);
 }
 
 static inline size_t lean_isize_land(size_t a1, size_t a2) {
diff --git a/stage0/src/stdlib_flags.h b/stage0/src/stdlib_flags.h
index 79a0e58edd..ed90dfb687 100644
--- a/stage0/src/stdlib_flags.h
+++ b/stage0/src/stdlib_flags.h
@@ -1,5 +1,7 @@
 #include "util/options.h"
 
+// I would like this to be regenerated please.
+
 namespace lean {
 options get_default_options() {
     options opts;
diff --git a/tests/lean/run/sint_div_overflow.lean b/tests/lean/run/sint_div_overflow.lean
index 8cc521b19f..ce2e084e7b 100644
--- a/tests/lean/run/sint_div_overflow.lean
+++ b/tests/lean/run/sint_div_overflow.lean
@@ -15,6 +15,7 @@ and 0 for mod.
 #guard (Int16.minValue / -1 : Int16) == Int16.minValue
 #guard (Int32.minValue / -1 : Int32) == Int32.minValue
 #guard (Int64.minValue / -1 : Int64) == Int64.minValue
+#guard (ISize.minValue / -1 : ISize) == ISize.minValue
 
 -- Test that signed mod handles overflow correctly
 -- INT_MIN % -1 should return 0
@@ -23,14 +24,17 @@ and 0 for mod.
 #guard (Int16.minValue % -1 : Int16) == 0
 #guard (Int32.minValue % -1 : Int32) == 0
 #guard (Int64.minValue % -1 : Int64) == 0
+#guard (ISize.minValue % -1 : ISize) == 0
 
 -- Also test via #eval to exercise the C runtime
 #eval (Int8.minValue / -1 : Int8)
 #eval (Int16.minValue / -1 : Int16)
 #eval (Int32.minValue / -1 : Int32)
 #eval (Int64.minValue / -1 : Int64)
+#eval (ISize.minValue / -1 : ISize)
 
 #eval (Int8.minValue % -1 : Int8)
 #eval (Int16.minValue % -1 : Int16)
 #eval (Int32.minValue % -1 : Int32)
 #eval (Int64.minValue % -1 : Int64)
+#eval (ISize.minValue % -1 : ISize)