diff --git a/80a9ab41b91ab849794bb7830f0a98d862c08269.diff b/80a9ab41b91ab849794bb7830f0a98d862c08269.diff
new file mode 100644
index 0000000..c05c376
--- /dev/null
+++ b/80a9ab41b91ab849794bb7830f0a98d862c08269.diff
@@ -0,0 +1,13 @@
+diff --git a/src/solver/modwrap.c b/src/solver/modwrap.c
+index a180dba649632c3d9c8d7e812a4bac3a60177d2d..124d4bc4b7b3b313f34deb223afc6267451bf974 100644
+--- a/src/solver/modwrap.c
++++ b/src/solver/modwrap.c
+@@ -18,6 +18,6 @@ char *solve_equation(const char *eq)
+         solve_equation_closure = caml_named_value("solve_equation");
+     }
+ 
+-    value v = copy_string(eq);
+-    return strdup(String_val(callback(*solve_equation_closure, v)));
++    value v = caml_copy_string(eq);
++    return strdup(String_val(caml_callback(*solve_equation_closure, v)));
+ }
diff --git a/kalzium.spec b/kalzium.spec
index 2ff2c96..9e7cd18 100644
--- a/kalzium.spec
+++ b/kalzium.spec
@@ -31,6 +31,7 @@ URL:     https://edu.kde.org/kalzium/
 Source0: http://download.kde.org/%{stable}/release-service/%{version}/src/%{name}-%{version}.tar.xz
 
 ## upstream patches
+Patch0: 80a9ab41b91ab849794bb7830f0a98d862c08269.diff
 
 %if ! 0%{?bootstrap}
 BuildRequires: libappstream-glib