diff --git a/coreapi/content.c b/coreapi/content.c
index 74d04ebb7..332789d2a 100644
--- a/coreapi/content.c
+++ b/coreapi/content.c
@@ -115,7 +115,7 @@ void linphone_content_set_buffer(LinphoneContent *content, const void *buffer, s
 	((char *)content->lcp.data)[size] = '\0';
 }
 
-char * linphone_content_get_string_buffer(const LinphoneContent *content) {
+const char * linphone_content_get_string_buffer(const LinphoneContent *content) {
 	return (char *)content->lcp.data;
 }
 
diff --git a/coreapi/content.h b/coreapi/content.h
index 400f5f5fb..e3e0166ce 100644
--- a/coreapi/content.h
+++ b/coreapi/content.h
@@ -165,7 +165,7 @@ LINPHONE_PUBLIC void linphone_content_set_buffer(LinphoneContent *content, const
  * @param[in] content LinphoneContent object
  * @return The string content data buffer.
  */
-LINPHONE_PUBLIC char * linphone_content_get_string_buffer(const LinphoneContent *content);
+LINPHONE_PUBLIC const char * linphone_content_get_string_buffer(const LinphoneContent *content);
 
 /**
  * Set the string content data buffer.
diff --git a/coreapi/linphonecore.c b/coreapi/linphonecore.c
index 6dc8aef36..152128a2c 100644
--- a/coreapi/linphonecore.c
+++ b/coreapi/linphonecore.c
@@ -7074,7 +7074,7 @@ int linphone_payload_type_get_normal_bitrate(const LinphonePayloadType *pt) {
 	return pt->normal_bitrate;
 }
 
-char * linphone_payload_type_get_mime_type(const LinphonePayloadType *pt) {
+const char * linphone_payload_type_get_mime_type(const LinphonePayloadType *pt) {
 	return pt->mime_type;
 }
 
diff --git a/coreapi/linphonecore.h b/coreapi/linphonecore.h
index 155170338..63ee7f7e0 100644
--- a/coreapi/linphonecore.h
+++ b/coreapi/linphonecore.h
@@ -257,7 +257,7 @@ LINPHONE_PUBLIC int linphone_payload_type_get_normal_bitrate(const LinphonePaylo
  * @param[in] pt LinphonePayloadType object
  * @return The mime type.
  */
-LINPHONE_PUBLIC char * linphone_payload_type_get_mime_type(const LinphonePayloadType *pt);
+LINPHONE_PUBLIC const char * linphone_payload_type_get_mime_type(const LinphonePayloadType *pt);
 
 /**
  * Get the number of channels.