diff --git a/pkgs/applications/misc/bambu-studio/default.nix b/pkgs/applications/misc/bambu-studio/default.nix
index 388b10f1356d..184ad1d8163e 100644
--- a/pkgs/applications/misc/bambu-studio/default.nix
+++ b/pkgs/applications/misc/bambu-studio/default.nix
@@ -34,7 +34,7 @@
   mesa,
   mpfr,
   nlopt,
-  opencascade-occt,
+  opencascade-occt_7_6,
   openvdb,
   pcre,
   qhull,
@@ -47,6 +47,7 @@
   withSystemd ? stdenv.isLinux,
 }:
 let
+  opencascade-occt = opencascade-occt_7_6;
   wxGTK31' = wxGTK31.overrideAttrs (old: {
     configureFlags = old.configureFlags ++ [
       # Disable noisy debug dialogs
diff --git a/pkgs/applications/misc/prusa-slicer/default.nix b/pkgs/applications/misc/prusa-slicer/default.nix
index b1e2a80617ba..96fc551595b5 100644
--- a/pkgs/applications/misc/prusa-slicer/default.nix
+++ b/pkgs/applications/misc/prusa-slicer/default.nix
@@ -23,7 +23,7 @@
 , mpfr
 , nanosvg
 , nlopt
-, opencascade-occt
+, opencascade-occt_7_6
 , openvdb
 , pcre
 , qhull
@@ -37,6 +37,7 @@
 , wxGTK-override ? null
 }:
 let
+  opencascade-occt = opencascade-occt_7_6;
   wxGTK-prusa = wxGTK32.overrideAttrs (old: rec {
     pname = "wxwidgets-prusa3d-patched";
     version = "3.2.0";
diff --git a/pkgs/applications/science/electronics/horizon-eda/base.nix b/pkgs/applications/science/electronics/horizon-eda/base.nix
index 8ce75a6ce241..2a37c0265dc3 100644
--- a/pkgs/applications/science/electronics/horizon-eda/base.nix
+++ b/pkgs/applications/science/electronics/horizon-eda/base.nix
@@ -9,12 +9,14 @@
 , libgit2
 , librsvg
 , libuuid
-, opencascade-occt
+, opencascade-occt_7_6
 , pkg-config
 , podofo
 , sqlite
 }:
-
+let
+  opencascade-occt = opencascade-occt_7_6;
+in
 # This base is used in horizon-eda and python3Packages.horizon-eda
 rec {
   pname = "horizon-eda";
diff --git a/pkgs/applications/science/electronics/kicad/base.nix b/pkgs/applications/science/electronics/kicad/base.nix
index 209d47875f8d..b5f721c3d772 100644
--- a/pkgs/applications/science/electronics/kicad/base.nix
+++ b/pkgs/applications/science/electronics/kicad/base.nix
@@ -42,7 +42,7 @@
 , swig4
 , python
 , wxPython
-, opencascade-occt
+, opencascade-occt_7_6
 , libngspice
 , valgrind
 
@@ -65,6 +65,7 @@ assert testing -> !stable
   -> throw "testing implies stable and cannot be used with stable = false";
 
 let
+  opencascade-occt = opencascade-occt_7_6;
   inherit (lib) optional optionals optionalString;
 in
 stdenv.mkDerivation rec {
diff --git a/pkgs/applications/science/physics/elmerfem/default.nix b/pkgs/applications/science/physics/elmerfem/default.nix
index e63203a93f28..c3720602d08d 100644
--- a/pkgs/applications/science/physics/elmerfem/default.nix
+++ b/pkgs/applications/science/physics/elmerfem/default.nix
@@ -1,5 +1,23 @@
-{ lib, stdenv, fetchFromGitHub, cmake, git, gfortran, mpi, blas, liblapack, pkg-config, libGL, libGLU, opencascade-occt, libsForQt5, tbb, vtkWithQt5 }:
-
+{ lib
+, stdenv
+, fetchFromGitHub
+, cmake
+, git
+, gfortran
+, mpi
+, blas
+, liblapack
+, pkg-config
+, libGL
+, libGLU
+, opencascade-occt_7_6
+, libsForQt5
+, tbb
+, vtkWithQt5
+}:
+let
+  opencascade-occt = opencascade-occt_7_6;
+in
 stdenv.mkDerivation rec {
   pname = "elmerfem";
   version = "unstable-2023-09-18";
@@ -19,6 +37,7 @@ stdenv.mkDerivation rec {
     pkg-config
     libsForQt5.wrapQtAppsHook
   ];
+
   buildInputs = [
     mpi
     blas
diff --git a/pkgs/by-name/fr/freecad/package.nix b/pkgs/by-name/fr/freecad/package.nix
index 61fa9a395e40..0e50640be212 100644
--- a/pkgs/by-name/fr/freecad/package.nix
+++ b/pkgs/by-name/fr/freecad/package.nix
@@ -19,7 +19,7 @@
 , mpi
 , ninja
 , ode
-, opencascade-occt
+, opencascade-occt_7_6
 , pkg-config
 , python3Packages
 , runCommand  # for passthru.tests
@@ -33,6 +33,7 @@
 }:
 
 let
+  opencascade-occt = opencascade-occt_7_6;
   boost = python3Packages.boost;
   inherit (libsForQt5)
     qtbase
diff --git a/pkgs/development/python-modules/ifcopenshell/default.nix b/pkgs/development/python-modules/ifcopenshell/default.nix
index 3fc63b13bb39..7288eb8d96bc 100644
--- a/pkgs/development/python-modules/ifcopenshell/default.nix
+++ b/pkgs/development/python-modules/ifcopenshell/default.nix
@@ -7,11 +7,13 @@
 , icu
 , swig
 , pcre
-, opencascade-occt
+, opencascade-occt_7_6
 , opencollada
 , libxml2
 }:
-
+let
+  opencascade-occt = opencascade-occt_7_6;
+in
 buildPythonPackage rec {
   pname = "ifcopenshell";
   version = "240306";