diff --git a/gas/config/tc-aarch64.c b/gas/config/tc-aarch64.c
index 77caba2f13996e541b1e5c216a980aa1b91e038e..89abdc62e4e97049856d6d22966b90ae147a52bf 100644
--- a/gas/config/tc-aarch64.c
+++ b/gas/config/tc-aarch64.c
@@ -2170,8 +2170,8 @@ s_aarch64_capinit (int ignored ATTRIBUTE_UNUSED)
       return;
     }
 
-  frag_grow (8);
-  fix_new_aarch64 (frag_now, frag_more (0) - frag_now->fr_literal, 8, &exp, 0,
+  frag_grow (16);
+  fix_new_aarch64 (frag_now, frag_more (0) - frag_now->fr_literal, 16, &exp, 0,
 		   BFD_RELOC_MORELLO_CAPINIT);
 
   demand_empty_rest_of_line ();
diff --git a/gas/testsuite/gas/aarch64/morello-capinit-require-size.d b/gas/testsuite/gas/aarch64/morello-capinit-require-size.d
new file mode 100644
index 0000000000000000000000000000000000000000..8a6370eccccc5ffe1300ef025029f8f81cee78cd
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/morello-capinit-require-size.d
@@ -0,0 +1,3 @@
+#name: Capinit Requires 16 bytes
+#as: -march=armv8-a+c64
+#error_output: morello-capinit-require-size.l
diff --git a/gas/testsuite/gas/aarch64/morello-capinit-require-size.l b/gas/testsuite/gas/aarch64/morello-capinit-require-size.l
new file mode 100644
index 0000000000000000000000000000000000000000..614213d95e9fa53a99f0c4591a58e56349e37d04
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/morello-capinit-require-size.l
@@ -0,0 +1,2 @@
+[^:]*: Assembler messages:
+[^:]*:7: Error: internal error: fixup not contained within frag
diff --git a/gas/testsuite/gas/aarch64/morello-capinit-require-size.s b/gas/testsuite/gas/aarch64/morello-capinit-require-size.s
new file mode 100644
index 0000000000000000000000000000000000000000..6931c4997da7d45da034c4ba6fafe5bfb0a6cef3
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/morello-capinit-require-size.s
@@ -0,0 +1,17 @@
+.data
+.align 4
+a:
+	.8byte 0
+
+d:
+	.capinit a
+	.8byte 0
+	.size d, .-d
+
+// Need to switch section so that the capinit relocation does not have enough
+// space in the relevant chunk.
+.section .data.rel.ro
+.align 4
+e:
+	.8byte 0
+	.size e, .-e