diff --git a/herwig7-fxfx-fix.patch b/herwig7-fxfx-fix.patch
new file mode 100644
index 00000000000..8d730633c41
--- /dev/null
+++ b/herwig7-fxfx-fix.patch
@@ -0,0 +1,35 @@
+diff --git a/MatrixElement/FxFx/FxFx.h b/MatrixElement/FxFx/FxFx.h
+index a2133bb..23eba40 100644
+--- a/MatrixElement/FxFx/FxFx.h
++++ b/MatrixElement/FxFx/FxFx.h
+@@ -161,7 +161,7 @@ public:
+     ISTUP.resize(NUP);
+     MOTHUP.resize(NUP);
+     ICOLUP.resize(NUP);
+-    PUP.resize(NUP, std::vector<double>(5));
++    PUP.resize(NUP);
+     VTIMUP.resize(NUP);
+     SPINUP.resize(NUP);
+   }
+@@ -231,7 +231,7 @@ public:
+    * Lab frame momentum (Px, Py, Pz, E and M in GeV) for the particle
+    * entries in this event.
+    */
+-  vector< vector<double> > PUP;
++  vector< array<double,5> > PUP;
+ 
+   /**
+    * Invariant lifetime (c*tau, distance from production to decay im
+diff --git a/MatrixElement/FxFx/FxFxReader.cc b/MatrixElement/FxFx/FxFxReader.cc
+index 3dafe2c..d2340cd 100644
+--- a/MatrixElement/FxFx/FxFxReader.cc
++++ b/MatrixElement/FxFx/FxFxReader.cc
+@@ -1219,7 +1219,7 @@ bool FxFxReader::uncacheEvent() {
+   pos = mread(pos, hepeup.MOTHUP[0], hepeup.NUP);
+   hepeup.ICOLUP.resize(hepeup.NUP);
+   pos = mread(pos, hepeup.ICOLUP[0], hepeup.NUP);
+-  hepeup.PUP.resize(hepeup.NUP, vector<double>(5));
++  hepeup.PUP.resize(hepeup.NUP);
+   for ( int i = 0; i < hepeup.NUP; ++i ) 
+     pos = mread(pos, hepeup.PUP[i][0], 5);
+   hepeup.VTIMUP.resize(hepeup.NUP);
diff --git a/herwig7.spec b/herwig7.spec
index 28eedee6b87..cfb55fcbd3b 100644
--- a/herwig7.spec
+++ b/herwig7.spec
@@ -16,10 +16,12 @@ Requires: openloops
 %endif
 BuildRequires: autotools
 Patch0: herwig_Matchbox_mg_py3
+Patch1: herwig7-fxfx-fix
 
 %prep
 %setup -q -n Herwig-%{realversion}
 %patch0 -p1
+%patch1 -p1
 
 # Regenerate build scripts
 autoreconf -fiv