diff --git a/pkgs/development/compilers/gcc/common/platform-flags.nix b/pkgs/development/compilers/gcc/common/platform-flags.nix
index bd5a72f96036..fc068c194d2b 100644
--- a/pkgs/development/compilers/gcc/common/platform-flags.nix
+++ b/pkgs/development/compilers/gcc/common/platform-flags.nix
@@ -10,7 +10,11 @@ in lib.concatLists [
   (lib.optional (p ? fpu) "--with-fpu=${p.fpu}")
   (lib.optional (p ? float) "--with-float=${p.float}")
   (lib.optional (p ? mode) "--with-mode=${p.mode}")
-  (lib.optional
-    (let tp = targetPlatform; in tp.isPower && tp.libc == "glibc" && tp.is64bit)
-    "--with-long-double-128")
+  (lib.optionals targetPlatform.isPower64
+    # musl explicitly rejects 128-bit long double on
+    # powerpc64; see musl/arch/powerpc64/bits/float.h
+    (lib.optionals (!targetPlatform.isMusl) [
+      "--with-long-double-128"
+      "--with-long-double-format=ieee"
+    ]))
 ]