diff --git a/ctools.pc.in b/ctools.pc.in
index b3eda26..1568860 100644
--- a/ctools.pc.in
+++ b/ctools.pc.in
@@ -8,7 +8,7 @@ Description: CTA science analysis tools
 URL: http://cta.irap.omp.eu/ctools
 Version: @VERSION@
 Requires: 
-Requires.private: gammalib >= 1.4.3
+Requires.private: gammalib == 1.4.3
 Conflicts: 
 Cflags: -I${includedir}/ctools @OPENMP_CXXFLAGS@
 Libs: -L${libdir} -lctools
diff --git a/dev/conda.recipe/meta.yaml.in b/dev/conda.recipe/meta.yaml.in
index 163fb0e..36bc4fd 100644
--- a/dev/conda.recipe/meta.yaml.in
+++ b/dev/conda.recipe/meta.yaml.in
@@ -18,10 +18,10 @@ requirements:
     - python  
     - setuptools
     - swig
-    - gammalib >=1.4.3
+    - gammalib ==1.4.3
   run:
     - python
-    - gammalib >=1.4.3
+    - gammalib ==1.4.3
 
 about:
   home: http://cta.irap.omp.eu/ctools