diff --git a/pjmedia/src/pjmedia-codec/gsm.c b/pjmedia/src/pjmedia-codec/gsm.c
index 3739ca7..2ecd03a 100644
--- a/pjmedia/src/pjmedia-codec/gsm.c
+++ b/pjmedia/src/pjmedia-codec/gsm.c
@@ -566,6 +566,7 @@
     }
 
     output->type = PJMEDIA_FRAME_TYPE_AUDIO;
+    output->timestamp = input->timestamp;
 
     return PJ_SUCCESS;
 }
@@ -595,6 +596,7 @@
 
     output->size = 320;
     output->type = PJMEDIA_FRAME_TYPE_AUDIO;
+    output->timestamp = input->timestamp;
 
 #if !PLC_DISABLED
     if (gsm_data->plc_enabled)