diff --git a/python-strictyaml.spec b/python-strictyaml.spec
index 466ae31..35c12aa 100644
--- a/python-strictyaml.spec
+++ b/python-strictyaml.spec
@@ -58,6 +58,9 @@ Provides:       bundled(python3dist(ruamel-yaml)) = 0.16.13
 %prep
 %forgesetup
 cp -p '%{SOURCE1}' .
+# Upstream’s idiosyncratic build system normally handles this:
+sed -r -i 's/(__version__ *= *")DEVELOPMENT_VERSION"/\1%{version}"/' \
+    'strictyaml/__init__.py'
 
 
 %generate_buildrequires