diff --git a/var/spack/repos/builtin/packages/ocaml/package.py b/var/spack/repos/builtin/packages/ocaml/package.py
index 4e642b9f56..66b2dc41e5 100644
--- a/var/spack/repos/builtin/packages/ocaml/package.py
+++ b/var/spack/repos/builtin/packages/ocaml/package.py
@@ -44,6 +44,17 @@ def install(self, spec, prefix):
         if self.spec.satisfies('~force-safe-string'):
             base_args += ['--disable-force-safe-string']
 
+        # This patch is aarch64-linux-fj only.
+        # However, similar patch is needed for other arch/OS/compiler
+        # to use correct assembler. (See #17918)
+        if self.spec.satisfies('%fj'):
+            filter_file(
+                '${toolpref}clang -c -Wno-trigraphs',
+                spack_cc + ' -c',
+                'configure',
+                string=True
+            )
+
         configure(*(base_args))
 
         make('world.opt')