diff --git a/src/classic/hsp_ag.c b/src/classic/hsp_ag.c
index 37d13e4bf..98274fa99 100644
--- a/src/classic/hsp_ag.c
+++ b/src/classic/hsp_ag.c
@@ -531,9 +531,8 @@ static void hsp_run(void){
                 int gain = hsp_ag_microphone_gain;
                 hsp_ag_microphone_gain = -1;
                 char buffer[12];
-                snprintf(buffer, sizeof(buffer), "\r\n%s=%d\r\n",
+                btstack_snprintf_assert_complete(buffer, sizeof(buffer), "\r\n%s=%d\r\n",
                          HSP_MICROPHONE_GAIN, gain);
-                buffer[sizeof(buffer) - 1] = 0;
                 hsp_ag_send_str_over_rfcomm(hsp_ag_rfcomm_cid, buffer);
                 break;
             }
@@ -546,9 +545,8 @@ static void hsp_run(void){
                 int gain = hsp_ag_speaker_gain;
                 hsp_ag_speaker_gain = -1;
                 char buffer[12];
-                snprintf(buffer, sizeof(buffer), "\r\n%s=%d\r\n",
+                btstack_snprintf_assert_complete(buffer, sizeof(buffer), "\r\n%s=%d\r\n",
                          HSP_SPEAKER_GAIN, gain);
-                buffer[sizeof(buffer) - 1] = 0;
                 hsp_ag_send_str_over_rfcomm(hsp_ag_rfcomm_cid, buffer);
                 break;
             }
diff --git a/src/classic/hsp_hs.c b/src/classic/hsp_hs.c
index 9718e0a96..6105b4d90 100644
--- a/src/classic/hsp_hs.c
+++ b/src/classic/hsp_hs.c
@@ -417,9 +417,8 @@ static void hsp_run_handle_state(void){
                     return;
                 }
                 char buffer[20];
-                snprintf(buffer, sizeof(buffer), "%s=%d\r",
+                btstack_snprintf_assert_complete(buffer, sizeof(buffer), "%s=%d\r",
                          HSP_HS_MICROPHONE_GAIN, hsp_hs_microphone_gain);
-                buffer[sizeof(buffer) - 1] = 0;
                 hsp_hs_send_str_over_rfcomm(hsp_hs_rfcomm_cid, buffer);
                 hsp_hs_microphone_gain = -1;
                 break;
@@ -431,9 +430,8 @@ static void hsp_run_handle_state(void){
                     return;
                 }
                 char buffer[20];
-                snprintf(buffer, sizeof(buffer), "%s=%d\r",
+                btstack_snprintf_assert_complete(buffer, sizeof(buffer), "%s=%d\r",
                          HSP_HS_SPEAKER_GAIN, hsp_hs_speaker_gain);
-                buffer[sizeof(buffer) - 1] = 0;
                 hsp_hs_send_str_over_rfcomm(hsp_hs_rfcomm_cid, buffer);
                 hsp_hs_speaker_gain = -1;
                 break;