Correct hyperlink

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/docs/3.0-migration-guide.md b/docs/3.0-migration-guide.md
index a6b71f6..e91211a 100644
--- a/docs/3.0-migration-guide.md
+++ b/docs/3.0-migration-guide.md
@@ -252,7 +252,7 @@
 
 ### GCM interface changes: impact for alternative implementations
 
-The GCM multipart interface has changed as described in [“GCM multipart interface: application changes”](#gcm-multipart-interface:-application-changes). The consequences for an alternative implementation of GCM (`MBEDTLS_GCM_ALT`) are as follows:
+The GCM multipart interface has changed as described in [“GCM multipart interface: application changes”](#gcm-multipart-interface-application-changes). The consequences for an alternative implementation of GCM (`MBEDTLS_GCM_ALT`) are as follows:
 
 * `mbedtls_gcm_starts()` now only sets the mode and the nonce (IV). The new function `mbedtls_gcm_update_ad()` receives the associated data. It may be called multiple times.
 * `mbedtls_gcm_update()` now allows arbitrary-length inputs, takes an extra parameter to indicate the actual output length. Alternative implementations may choose between two modes: