diff --git a/org.kde.kcalc.json b/org.kde.kcalc.json
--- a/org.kde.kcalc.json
+++ b/org.kde.kcalc.json
@@ -10,6 +10,16 @@
     "finish-args": ["--share=ipc", "--socket=x11", "--socket=wayland", "--filesystem=host" ],
 
     "modules": [
+        {
+            "name": "mpfr",
+            "sources": [
+                {
+                    "type": "archive",
+                    "url": "https://www.mpfr.org/mpfr-current/mpfr-4.0.2.tar.xz",
+                    "sha256": "1d3be708604eae0e42d578ba93b390c2a145f17743a744d8f3f8c2ad5855a38a"
+                }
+            ]
+        },
         {
             "name": "kcalc",
             "buildsystem": "cmake-ninja",