diff --git a/tests/compile-fail/transmute_fat.rs b/tests/compile-fail/transmute_fat.rs
new file mode 100644
index 000000000000..6b9e6f876481
--- /dev/null
+++ b/tests/compile-fail/transmute_fat.rs
@@ -0,0 +1,13 @@
+#![feature(i128_type)]
+
+fn main() {
+    #[cfg(target_pointer_width="64")]
+    let bad = unsafe {
+        std::mem::transmute::<&[u8], u128>(&[1u8])
+    };
+    #[cfg(target_pointer_width="32")]
+    let bad = unsafe {
+        std::mem::transmute::<&[u8], u64>(&[1u8])
+    };
+    bad + 1; //~ ERROR a raw memory access tried to access part of a pointer value as raw bytes
+}
diff --git a/tests/compile-fail/transmute_fat2.rs b/tests/compile-fail/transmute_fat2.rs
new file mode 100644
index 000000000000..028ed613eee7
--- /dev/null
+++ b/tests/compile-fail/transmute_fat2.rs
@@ -0,0 +1,13 @@
+#![feature(i128_type)]
+
+fn main() {
+    #[cfg(target_pointer_width="64")]
+    let bad = unsafe {
+        std::mem::transmute::<u128, &[u8]>(42)
+    };
+    #[cfg(target_pointer_width="32")]
+    let bad = unsafe {
+        std::mem::transmute::<u64, &[u8]>(42)
+    };
+    bad[0]; //~ ERROR index out of bounds: the len is 0 but the index is 0
+}