diff --git a/pkgs/by-name/li/libagar/fix-conflicting-types.patch b/pkgs/by-name/li/libagar/fix-conflicting-types.patch
new file mode 100644
index 000000000000..0de03c279f4e
--- /dev/null
+++ b/pkgs/by-name/li/libagar/fix-conflicting-types.patch
@@ -0,0 +1,26 @@
+--- a/math/m_sparse_factor.c
++++ b/math/m_sparse_factor.c
+@@ -1236,7 +1236,6 @@ int  I, NumberOfTies = 0;
+ ElementPtr  ChosenPivot, TiedElements[MAX_MARKOWITZ_TIES + 1];
+ RealNumber  Magnitude, LargestInCol, Ratio, MaxRatio;
+ RealNumber  LargestOffDiagonal;
+-RealNumber  FindBiggestInColExclude();
+ 
+ /* Begin `QuicklySearchDiagonal'. */
+     NumberOfTies = -1;
+@@ -1434,7 +1433,6 @@ register  ElementPtr  pDiag;
+ int  I;
+ ElementPtr  ChosenPivot, pOtherInRow, pOtherInCol;
+ RealNumber  Magnitude, LargestInCol, LargestOffDiagonal;
+-RealNumber  FindBiggestInColExclude();
+ 
+ /* Begin `QuicklySearchDiagonal'. */
+     ChosenPivot = NULL;
+@@ -1601,7 +1599,6 @@ register  ElementPtr  pDiag;
+ int  NumberOfTies = 0, Size = Matrix->Size;
+ ElementPtr  ChosenPivot;
+ RealNumber  Magnitude, Ratio, RatioOfAccepted = 0.0, LargestInCol;
+-RealNumber  FindBiggestInColExclude();
+ 
+ /* Begin `SearchDiagonal'. */
+     ChosenPivot = NULL;
diff --git a/pkgs/by-name/li/libagar/package.nix b/pkgs/by-name/li/libagar/package.nix
index 0335ab5a37a1..b9d5f912180f 100644
--- a/pkgs/by-name/li/libagar/package.nix
+++ b/pkgs/by-name/li/libagar/package.nix
@@ -29,6 +29,10 @@ stdenv.mkDerivation (finalAttrs: {
     sha256 = "001wcqk5z67qg0raw9zlwmv62drxiwqykvsbk10q2mrc6knjsd42";
   };
 
+  patches = [
+    ./fix-conflicting-types.patch
+  ];
+
   preConfigure = ''
     substituteInPlace configure.in \
       --replace '_BSD_SOURCE' '_DEFAULT_SOURCE'