diff --git a/pkgs/development/libraries/tachyon/default.nix b/pkgs/development/libraries/tachyon/default.nix
index 10b12c5b558..47cebd62df6 100644
--- a/pkgs/development/libraries/tachyon/default.nix
+++ b/pkgs/development/libraries/tachyon/default.nix
@@ -36,8 +36,11 @@ stdenv.mkDerivation rec {
   '';
   arch = if stdenv.hostPlatform.system == "x86_64-linux"   then "linux-64-thr"  else
          if stdenv.hostPlatform.system == "i686-linux"     then "linux-thr"     else
-         if stdenv.hostPlatform.system == "aarch64-linux"  then "linux-arm-thr" else
-         if stdenv.hostPlatform.system == "armv7l-linux"   then "linux-arm-thr" else
+         # 2021-03-29: multithread (-DTHR -D_REENTRANT) was disabled on linux-arm
+         # because it caused Sage's 3D plotting tests to hang indefinitely.
+         # see https://github.com/NixOS/nixpkgs/pull/117465
+         if stdenv.hostPlatform.system == "aarch64-linux"  then "linux-arm"     else
+         if stdenv.hostPlatform.system == "armv7l-linux"   then "linux-arm"     else
          if stdenv.hostPlatform.system == "x86_64-darwin"  then "macosx-thr"    else
          if stdenv.hostPlatform.system == "i686-darwin"    then "macosx-64-thr" else
          if stdenv.hostPlatform.system == "i686-cygwin"    then "win32"         else
diff --git a/pkgs/development/libraries/tachyon/make-archs.patch b/pkgs/development/libraries/tachyon/make-archs.patch
index cf83f8c8c31..ee81681e101 100644
--- a/pkgs/development/libraries/tachyon/make-archs.patch
+++ b/pkgs/development/libraries/tachyon/make-archs.patch
@@ -22,11 +22,11 @@ index 08afb85..dbeb691 100644
  	"RANLIB = ranlib" \
  	"LIBS = -L. -ltachyon $(MISCLIB) -lm -lpthread"
  
-+# Linux Arm using gcc, with threads
-+linux-arm-thr:
++# Linux Arm using gcc
++linux-arm:
 +	$(MAKE) all \
-+	"ARCH = linux-arm-thr" \
-+	"CFLAGS = -Wall -O3 -fomit-frame-pointer -ffast-math -DLinux -DTHR -D_REENTRANT $(MISCFLAGS)" \
++	"ARCH = linux-arm" \
++	"CFLAGS = -Wall -O3 -fomit-frame-pointer -ffast-math -DLinux $(MISCFLAGS)" \
 +	"ARFLAGS = r" \
 +	"STRIP = strip" \
 +	"RANLIB = ranlib" \