diff --git a/gub/specs/fontforge.py b/gub/specs/fontforge.py
index 6744dbe2c..3a6c2857f 100644
--- a/gub/specs/fontforge.py
+++ b/gub/specs/fontforge.py
@@ -8,4 +8,5 @@ class Fontforge__tools (tools.AutoBuild):
     configure_flags = (tools.AutoBuild.configure_flags
                 + ' --without-cairo '
                 + ' --without-x '
-                + ' --enable-python-scripting=3 ')
+                + ' --enable-python-scripting=3 '
+                + ' PYTHON=%(tools_prefix)s/bin/python3 ')
diff --git a/gub/specs/lilypond-test.py b/gub/specs/lilypond-test.py
index b1216ff5f..a1cc80042 100644
--- a/gub/specs/lilypond-test.py
+++ b/gub/specs/lilypond-test.py
@@ -7,6 +7,7 @@
 class LilyPond_test (lilypond.LilyPond_base):
     dependencies = (lilypond.LilyPond_base.dependencies
                 + [
+                'tools::imagemagick',
                 'tools::netpbm',
                 'tools::fonts-dejavu',
                 'tools::fonts-libertine',
diff --git a/gub/specs/p7zip.py b/gub/specs/p7zip.py
index f4919f033..2de8fb598 100644
--- a/gub/specs/p7zip.py
+++ b/gub/specs/p7zip.py
@@ -2,6 +2,7 @@
 
 class P7zip__tools (tools.MakeBuild):
     source = 'http://sourceforge.net/projects/p7zip/files/p7zip/9.20.1/p7zip_9.20.1_src_all.tar.bz2'
+    patches = [ 'p7zip-gcc10-conversion.patch' ]
     dependencies = [ 'bzip2', 'system::g++' ]
     install_flags = ' DEST_HOME=%(install_prefix)s install'
     def patch (self):
diff --git a/patches/p7zip-gcc10-conversion.patch b/patches/p7zip-gcc10-conversion.patch
new file mode 100644
index 000000000..4afb145a3
--- /dev/null
+++ b/patches/p7zip-gcc10-conversion.patch
@@ -0,0 +1,25 @@
+--- p7zip-9.20.1.src.all.orig/CPP/Windows/Error.cpp	2020-07-25 15:25:33.720387509 +0200
++++ p7zip-9.20.1.src.all/CPP/Windows/Error.cpp	2020-07-25 15:26:56.104520466 +0200
+@@ -14,14 +14,14 @@
+   AString msg;
+ 
+   switch(messageID) {
+-    case ERROR_NO_MORE_FILES   : txt = "No more files"; break ;
+-    case E_NOTIMPL             : txt = "E_NOTIMPL"; break ;
+-    case E_NOINTERFACE         : txt = "E_NOINTERFACE"; break ;
+-    case E_ABORT               : txt = "E_ABORT"; break ;
+-    case E_FAIL                : txt = "E_FAIL"; break ;
+-    case STG_E_INVALIDFUNCTION : txt = "STG_E_INVALIDFUNCTION"; break ;
+-    case E_OUTOFMEMORY         : txt = "E_OUTOFMEMORY"; break ;
+-    case E_INVALIDARG          : txt = "E_INVALIDARG"; break ;
++    case unsigned (ERROR_NO_MORE_FILES)   : txt = "No more files"; break ;
++    case unsigned (E_NOTIMPL)             : txt = "E_NOTIMPL"; break ;
++    case unsigned (E_NOINTERFACE)         : txt = "E_NOINTERFACE"; break ;
++    case unsigned (E_ABORT)               : txt = "E_ABORT"; break ;
++    case unsigned (E_FAIL)                : txt = "E_FAIL"; break ;
++    case unsigned (STG_E_INVALIDFUNCTION) : txt = "STG_E_INVALIDFUNCTION"; break ;
++    case unsigned (E_OUTOFMEMORY)         : txt = "E_OUTOFMEMORY"; break ;
++    case unsigned (E_INVALIDARG)          : txt = "E_INVALIDARG"; break ;
+     default:
+       txt = strerror(messageID);
+   }