diff --git a/src/include/units/bits/ratio_maths.h b/src/include/units/bits/ratio_maths.h
index 79b8aa30..145f6746 100644
--- a/src/include/units/bits/ratio_maths.h
+++ b/src/include/units/bits/ratio_maths.h
@@ -30,7 +30,7 @@
 #include <numeric>
 #include <tuple>
 #include <type_traits>
-#include <gsl/gsl>
+#include <gsl/gsl_assert>
 
 namespace units::detail {
 
diff --git a/src/include/units/symbol_text.h b/src/include/units/symbol_text.h
index e603b491..9ade00d2 100644
--- a/src/include/units/symbol_text.h
+++ b/src/include/units/symbol_text.h
@@ -2,7 +2,7 @@
 
 #include <units/bits/external/fixed_string.h>
 #include <units/bits/external/hacks.h>
-#include <gsl/gsl>
+#include <gsl/gsl_assert>
 
 namespace units {