diff --git a/lib/std/Target.zig b/lib/std/Target.zig
index 4a0ef36718..64608181fc 100644
--- a/lib/std/Target.zig
+++ b/lib/std/Target.zig
@@ -2303,7 +2303,9 @@ pub fn c_type_bit_size(target: Target, c_type: CType) u16 {
             .short, .ushort => return 16,
             .int, .uint, .float => return 32,
             .long, .ulong, .longlong, .ulonglong, .double => return 64,
-            .longdouble => return 64,
+            // Note: The OpenCL specification does not guarantee a particular size for long double,
+            // but clang uses 128 bits.
+            .longdouble => return 128,
         },
 
         .ps4, .ps5 => switch (c_type) {