diff --git a/CODING_CONVENTIONS.md b/CODING_CONVENTIONS.md
index 24e6c05953..f39db60f6e 100644
--- a/CODING_CONVENTIONS.md
+++ b/CODING_CONVENTIONS.md
@@ -2,7 +2,7 @@
 
 ## General
 
-* Code shall be [C99](http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf)
+* Code shall be [C11](http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf)
   compliant.
 * Avoid dynamic memory allocation (malloc/free, new, etc.)! It will break
   real-time guarantees, increase code complexity, and make it more likely to use
diff --git a/boards/native/Makefile.include b/boards/native/Makefile.include
index 98de7a2fea..9c08c7d8b9 100644
--- a/boards/native/Makefile.include
+++ b/boards/native/Makefile.include
@@ -23,7 +23,7 @@ export GPROF ?= gprof
 CFLAGS += -Wall -Wextra -pedantic $(CFLAGS_DBG)
 CFLAGS_DBG ?= -g3
 
-# default std set to gnu99 of not overwritten by user
+# default std set to gnu11 if not overwritten by user
 ifeq (,$(filter -std=%, $(CFLAGS)))
   CFLAGS += -std=gnu11
 endif
diff --git a/makefiles/cflags.inc.mk b/makefiles/cflags.inc.mk
index 0fb5fcc512..d68ea018d0 100644
--- a/makefiles/cflags.inc.mk
+++ b/makefiles/cflags.inc.mk
@@ -1,8 +1,8 @@
 # Test if the input language was specified externally.
-# Otherwise test if the compiler unterstands the "-std=c99" flag, and use it if so.
+# Otherwise test if the compiler unterstands the "-std=c11" flag, and use it if so.
 ifeq ($(filter -std=%,$(CFLAGS)),)
-  ifeq ($(shell $(CC) -std=c99 -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
-    CFLAGS += -std=c99
+  ifeq ($(shell $(CC) -std=c11 -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
+    CFLAGS += -std=c11
   endif
 endif
 
diff --git a/pkg/relic/Makefile b/pkg/relic/Makefile
index c4625e1eb3..e2c8bbd656 100644
--- a/pkg/relic/Makefile
+++ b/pkg/relic/Makefile
@@ -29,7 +29,7 @@ $(PKG_BUILD_DIR)/lib/librelic_s.a: $(PKG_BUILD_DIR)/Makefile
 
 # Pass 'COMP' with a target specific export to not have issues with the shell
 # escaping evaluation.
-COMP = $(filter-out -Werror -Werror=old-style-definition -Werror=strict-prototypes -std=gnu99,$(CFLAGS))
+COMP = $(filter-out -Werror -Werror=old-style-definition -Werror=strict-prototypes -std=gnu11,$(CFLAGS))
 $(PKG_BUILD_DIR)/Makefile: export COMP ?=
 $(PKG_BUILD_DIR)/Makefile: $(PKG_PREPARED) $(TOOLCHAIN_FILE) | ..cmake_version_supported
 	cmake -B$(PKG_BUILD_DIR) -H$(PKG_SOURCE_DIR) \