diff --git a/build/pkgs/singular/patches/0001-factory-canonicalform.h-Add-more-FACTORY_PUBLIC.patch b/build/pkgs/singular/patches/0001-factory-canonicalform.h-Add-more-FACTORY_PUBLIC.patch
new file mode 100644
index 00000000000..7f083e9e869
--- /dev/null
+++ b/build/pkgs/singular/patches/0001-factory-canonicalform.h-Add-more-FACTORY_PUBLIC.patch
@@ -0,0 +1,97 @@
+From 5830ce6deabefaeaec492f1054cc619af4e4e2d2 Mon Sep 17 00:00:00 2001
+From: Matthias Koeppe <mkoeppe@math.ucdavis.edu>
+Date: Tue, 20 Jul 2021 19:19:32 -0700
+Subject: [PATCH] factory/canonicalform.h: Add more FACTORY_PUBLIC
+
+---
+ factory/canonicalform.h | 42 ++++++++++++++++++++---------------------
+ 1 file changed, 21 insertions(+), 21 deletions(-)
+
+diff --git a/factory/canonicalform.h b/factory/canonicalform.h
+index 82dfa57e1..8fd158385 100644
+--- a/factory/canonicalform.h
++++ b/factory/canonicalform.h
+@@ -172,27 +172,27 @@ public:
+     int ilog2() const;
+ 
+     // comparison operators
+-    friend bool operator == ( const CanonicalForm&, const CanonicalForm& );
+-    friend bool operator != ( const CanonicalForm&, const CanonicalForm& );
+-    friend bool operator > ( const CanonicalForm&, const CanonicalForm& );
+-    friend bool operator < ( const CanonicalForm&, const CanonicalForm& );
++    friend FACTORY_PUBLIC bool operator == ( const CanonicalForm&, const CanonicalForm& );
++    friend FACTORY_PUBLIC bool operator != ( const CanonicalForm&, const CanonicalForm& );
++    friend FACTORY_PUBLIC bool operator > ( const CanonicalForm&, const CanonicalForm& );
++    friend FACTORY_PUBLIC bool operator < ( const CanonicalForm&, const CanonicalForm& );
+ 
+     // arithmetic operators
+-    friend CF_NO_INLINE CanonicalForm operator - ( const CanonicalForm& );
++    friend CF_NO_INLINE FACTORY_PUBLIC CanonicalForm operator - ( const CanonicalForm& );
+ 
+-    friend void FACTORY_PUBLIC divrem ( const CanonicalForm&, const CanonicalForm&, CanonicalForm&, CanonicalForm& );
+-    friend bool divremt ( const CanonicalForm&, const CanonicalForm&, CanonicalForm&, CanonicalForm& );
+-    friend bool tryDivremt ( const CanonicalForm&, const CanonicalForm&, CanonicalForm&, CanonicalForm&, const CanonicalForm&, bool& );
++    friend FACTORY_PUBLIC void divrem ( const CanonicalForm&, const CanonicalForm&, CanonicalForm&, CanonicalForm& );
++    friend FACTORY_PUBLIC bool divremt ( const CanonicalForm&, const CanonicalForm&, CanonicalForm&, CanonicalForm& );
++    friend FACTORY_PUBLIC bool tryDivremt ( const CanonicalForm&, const CanonicalForm&, CanonicalForm&, CanonicalForm&, const CanonicalForm&, bool& );
+ 
+-    friend CanonicalForm bgcd ( const CanonicalForm &, const CanonicalForm & );
+-    friend CanonicalForm bextgcd ( const CanonicalForm &, const CanonicalForm &, CanonicalForm &, CanonicalForm & );
++    friend FACTORY_PUBLIC CanonicalForm bgcd ( const CanonicalForm &, const CanonicalForm & );
++    friend FACTORY_PUBLIC CanonicalForm bextgcd ( const CanonicalForm &, const CanonicalForm &, CanonicalForm &, CanonicalForm & );
+ 
+     // input/output
+ #ifndef NOSTREAMIO
+    void print( OSTREAM&, char * ) const;
+    void print( OSTREAM& ) const;
+-   friend OSTREAM& operator << ( OSTREAM&, const CanonicalForm& );
+-   friend ISTREAM& operator >> ( ISTREAM&, CanonicalForm& );
++   friend FACTORY_PUBLIC OSTREAM& operator << ( OSTREAM&, const CanonicalForm& );
++   friend FACTORY_PUBLIC ISTREAM& operator >> ( ISTREAM&, CanonicalForm& );
+ #endif /* NOSTREAMIO */
+ 
+     // obsolete methods
+@@ -234,7 +234,7 @@ mod ( const CanonicalForm&, const CanonicalForm& );
+ /*BEGINPUBLIC*/
+ 
+ //{{{ function declarations from canonicalform.cc
+-CanonicalForm blcm ( const CanonicalForm & f, const CanonicalForm & g );
++CanonicalForm FACTORY_PUBLIC blcm ( const CanonicalForm & f, const CanonicalForm & g );
+ 
+ CanonicalForm FACTORY_PUBLIC power ( const CanonicalForm & f, int n );
+ 
+@@ -244,23 +244,23 @@ CanonicalForm FACTORY_PUBLIC power ( const Variable & v, int n );
+ //{{{ function declarations from cf_gcd.cc
+ CanonicalForm FACTORY_PUBLIC gcd ( const CanonicalForm&, const CanonicalForm& );
+ 
+-CanonicalForm gcd_poly ( const CanonicalForm & f, const CanonicalForm & g );
++CanonicalForm FACTORY_PUBLIC gcd_poly ( const CanonicalForm & f, const CanonicalForm & g );
+ 
+-CanonicalForm lcm ( const CanonicalForm&, const CanonicalForm& );
++CanonicalForm FACTORY_PUBLIC lcm ( const CanonicalForm&, const CanonicalForm& );
+ 
+-CanonicalForm pp ( const CanonicalForm& );
++CanonicalForm FACTORY_PUBLIC pp ( const CanonicalForm& );
+ 
+-CanonicalForm content ( const CanonicalForm& );
++CanonicalForm FACTORY_PUBLIC content ( const CanonicalForm& );
+ 
+-CanonicalForm content ( const CanonicalForm&, const Variable& );
++CanonicalForm FACTORY_PUBLIC content ( const CanonicalForm&, const Variable& );
+ 
+-CanonicalForm icontent ( const CanonicalForm & f );
++CanonicalForm FACTORY_PUBLIC icontent ( const CanonicalForm & f );
+ 
+-CanonicalForm vcontent ( const CanonicalForm & f, const Variable & x );
++CanonicalForm FACTORY_PUBLIC vcontent ( const CanonicalForm & f, const Variable & x );
+ //}}}
+ 
+ //{{{ function declarations from cf_ops.cc
+-CanonicalForm swapvar ( const CanonicalForm &, const Variable &, const Variable & );
++CanonicalForm FACTORY_PUBLIC swapvar ( const CanonicalForm &, const Variable &, const Variable & );
+ 
+ CanonicalForm FACTORY_PUBLIC replacevar ( const CanonicalForm &, const Variable &, const Variable & );
+ 
+-- 
+2.31.1
+