diff --git a/lib/zig.h b/lib/zig.h
index dff143e1a3..0d51b6496f 100644
--- a/lib/zig.h
+++ b/lib/zig.h
@@ -1871,11 +1871,13 @@ typedef zig_i32 zig_f32;
 #define zig_bitSizeOf_f64 64
 #define zig_libc_name_f64(name) name
 #if _MSC_VER
+#ifdef ZIG_TARGET_ABI_MSVC
 #define zig_bitSizeOf_c_longdouble 64
-#define zig_as_special_constant_f64(sign, name, arg, repr) sign zig_as_f64(zig_msvc_flt_##name, )
-#else
-#define zig_as_special_constant_f64(sign, name, arg, repr) zig_as_special_f64(sign, name, arg, repr)
 #endif
+#define zig_as_special_constant_f64(sign, name, arg, repr) sign zig_as_f64(zig_msvc_flt_##name, )
+#else /* _MSC_VER */
+#define zig_as_special_constant_f64(sign, name, arg, repr) zig_as_special_f64(sign, name, arg, repr)
+#endif /* _MSC_VER */
 #if FLT_MANT_DIG == 53
 typedef float zig_f64;
 #define zig_as_f64(fp, repr) fp##f
@@ -1977,16 +1979,32 @@ typedef zig_i128 zig_f128;
 #endif
 
 #define zig_has_c_longdouble 1
+
+#ifdef ZIG_TARGET_ABI_MSVC
+#define zig_libc_name_c_longdouble(name) name
+#else
 #define zig_libc_name_c_longdouble(name) name##l
+#endif
+
 #define zig_as_special_constant_c_longdouble(sign, name, arg, repr) zig_as_special_c_longdouble(sign, name, arg, repr)
 #ifdef zig_bitSizeOf_c_longdouble
+
+#ifdef ZIG_TARGET_ABI_MSVC
+typedef double zig_c_longdouble;
+#undef zig_bitSizeOf_c_longdouble
+#define zig_bitSizeOf_c_longdouble 64
+#define zig_as_c_longdouble(fp, repr) fp
+#else
 typedef long double zig_c_longdouble;
 #define zig_as_c_longdouble(fp, repr) fp##l
-#else
+#endif
+
+#else /* zig_bitSizeOf_c_longdouble */
+
 #undef zig_has_c_longdouble
+#define zig_has_c_longdouble 0
 #define zig_bitSizeOf_c_longdouble 80
 #define zig_compiler_rt_abbrev_c_longdouble zig_compiler_rt_abbrev_f80
-#define zig_has_c_longdouble 0
 #define zig_repr_c_longdouble i128
 typedef zig_i128 zig_c_longdouble;
 #define zig_as_c_longdouble(fp, repr) repr
@@ -1994,7 +2012,8 @@ typedef zig_i128 zig_c_longdouble;
 #define zig_as_special_c_longdouble(sign, name, arg, repr) repr
 #undef zig_as_special_constant_c_longdouble
 #define zig_as_special_constant_c_longdouble(sign, name, arg, repr) repr
-#endif
+
+#endif /* zig_bitSizeOf_c_longdouble */
 
 #if !zig_has_float_builtins
 #define zig_float_from_repr(Type, ReprType) \
diff --git a/src/link/C.zig b/src/link/C.zig
index ad50a20b99..8b05b8b22d 100644
--- a/src/link/C.zig
+++ b/src/link/C.zig
@@ -231,6 +231,13 @@ pub fn flush(self: *C, comp: *Compilation, prog_node: *std.Progress.Node) !void
     return self.flushModule(comp, prog_node);
 }
 
+fn abiDefine(comp: *Compilation) ?[]const u8 {
+    return switch (comp.getTarget().abi) {
+        .msvc => "#define ZIG_TARGET_ABI_MSVC\n",
+        else => null,
+    };
+}
+
 pub fn flushModule(self: *C, comp: *Compilation, prog_node: *std.Progress.Node) !void {
     const tracy = trace(@src());
     defer tracy.end();
@@ -248,9 +255,14 @@ pub fn flushModule(self: *C, comp: *Compilation, prog_node: *std.Progress.Node)
     var f: Flush = .{};
     defer f.deinit(gpa);
 
-    // Covers zig.h, typedef, and asm.
-    try f.all_buffers.ensureUnusedCapacity(gpa, 2);
+    const abi_define = abiDefine(comp);
 
+    // Covers defines, zig.h, typedef, and asm.
+    var buf_count: usize = 2;
+    if (abi_define != null) buf_count += 1;
+    try f.all_buffers.ensureUnusedCapacity(gpa, buf_count);
+
+    if (abi_define) |buf| f.appendBufAssumeCapacity(buf);
     f.appendBufAssumeCapacity(zig_h);
 
     const typedef_index = f.all_buffers.items.len;