diff --git a/gnu/local.mk b/gnu/local.mk
index ea8a203ac9..706725965b 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -46,6 +46,7 @@
 # Copyright © 2021 Sharlatan Hellseher <sharlatanus@gmail.com>
 # Copyright © 2021 Dmitry Polyakov <polyakov@liltechdude.xyz>
 # Copyright © 2021 Andrew Tropin <andrew@trop.in>
+# Copyright © 2021 Simon Tournier <zimon.toutoune@gmail.com>
 #
 # This file is part of GNU Guix.
 #
@@ -1296,6 +1297,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/jfsutils-include-systypes.patch		\
   %D%/packages/patches/julia-SOURCE_DATE_EPOCH-mtime.patch	\
   %D%/packages/patches/julia-tracker-16-compat.patch		\
+  %D%/packages/patches/julia-allow-parallel-build.patch		\
   %D%/packages/patches/kdbusaddons-kinit-file-name.patch	\
   %D%/packages/patches/libffi-3.3-powerpc-fixes.patch		\
   %D%/packages/patches/libffi-float128-powerpc64le.patch	\
diff --git a/gnu/packages/julia.scm b/gnu/packages/julia.scm
index d0329a96a1..ac5bf7db25 100644
--- a/gnu/packages/julia.scm
+++ b/gnu/packages/julia.scm
@@ -145,7 +145,8 @@ libraries.  It is also a bit like @code{ldd} and @code{otool -L}.")
                (base32
                 "1515x8fs25l3f9csbmd1v4nm041zvjnvigy6s5iidy4yrkwdx4r5"))
               (patches
-               (search-patches "julia-SOURCE_DATE_EPOCH-mtime.patch"))))
+               (search-patches "julia-SOURCE_DATE_EPOCH-mtime.patch"
+                               "julia-allow-parallel-build.patch"))))
     (build-system gnu-build-system)
     (arguments
      `(#:test-target "test"
diff --git a/gnu/packages/patches/julia-allow-parallel-build.patch b/gnu/packages/patches/julia-allow-parallel-build.patch
new file mode 100644
index 0000000000..5a382e7c89
--- /dev/null
+++ b/gnu/packages/patches/julia-allow-parallel-build.patch
@@ -0,0 +1,30 @@
+diff --git a/test/runtests.jl b/test/runtests.jl
+index 2f9cd058bb..150395e78c 100644
+--- a/test/runtests.jl
++++ b/test/runtests.jl
+@@ -4,7 +4,7 @@ using Test
+ using Distributed
+ using Dates
+ import REPL
+-using Printf: @sprintf
++using Printf: @sprintf, @printf
+ using Base: Experimental
+ 
+ include("choosetests.jl")
+@@ -83,11 +83,15 @@ prepend!(tests, linalg_tests)
+ import LinearAlgebra
+ cd(@__DIR__) do
+     n = 1
+-    if net_on
++    # Allow parallel tests with isolated environment
++    # https://github.com/JuliaLang/julia/issues/43205
++    # https://github.com/JuliaLang/julia/pull/43211
++    if net_on || haskey(ENV, "JULIA_CPU_THREADS")
+         n = min(Sys.CPU_THREADS, length(tests))
+         n > 1 && addprocs_with_testenv(n)
+         LinearAlgebra.BLAS.set_num_threads(1)
+     end
++    @printf("Number of threads: %i\n", n)
+     skipped = 0
+ 
+     @everywhere include("testdefs.jl")