diff --git a/lib/Test2/Harness/Runner/Job.pm b/lib/Test2/Harness/Runner/Job.pm
index 866db0846..b47884e76 100644
--- a/lib/Test2/Harness/Runner/Job.pm
+++ b/lib/Test2/Harness/Runner/Job.pm
@@ -511,7 +511,7 @@ sub env_vars {
     my $from_task = $self->{+TASK}->{env_vars};
 
     my @p5l = ($from_task->{PERL5LIB}, $from_run->{PERL5LIB});
-    push @p5l => $self->includes if $self->{+TASK}->{binary} || $self->{+TASK}->{non_perl};
+    push @p5l => $self->includes;
     push @p5l => $ENV{PERL5LIB} if $ENV{PERL5LIB};
     my $p5l = join $Config{path_sep} => grep { defined $_ && $_ ne '.' } @p5l;
 
diff --git a/t/integration/includes.t b/t/integration/includes.t
index a0f355ff0..6eabc4b03 100644
--- a/t/integration/includes.t
+++ b/t/integration/includes.t
@@ -52,4 +52,10 @@ yath(
     exit    => 0,
 ) if can_run('bash');
 
+yath(
+    command => 'test',
+    args    => ['child-inherits-inc.tx'],
+    exit    => 0,
+);
+
 done_testing;
diff --git a/t/integration/includes/child-inherits-inc.tx b/t/integration/includes/child-inherits-inc.tx
new file mode 100644
index 000000000..98c94c9a7
--- /dev/null
+++ b/t/integration/includes/child-inherits-inc.tx
@@ -0,0 +1,27 @@
+use Test2::V0;
+
+use File::Spec;
+use Config qw/%Config/;
+
+# This test verifies that child processes spawned via system() inherit
+# the include paths set by yath (fixes GitHub #296).
+# When yath runs a test with --lib, the test process gets -I flags on
+# the command line. But system($^X, ...) children don't inherit CLI flags;
+# they need PERL5LIB to find project modules.
+
+my @parts = File::Spec->splitpath(File::Spec->rel2abs(__FILE__));
+pop @parts;
+my $path = File::Spec->catpath(@parts);
+
+my $lib_dir = File::Spec->catdir($path, 'lib');
+
+# Spawn a child perl process and capture its @INC
+my $child_inc = `$^X -e "print join qq{\\n}, \@INC"`;
+my @child_inc = split /\n/, $child_inc;
+
+ok(
+    (grep { $_ eq $lib_dir } @child_inc),
+    "Child process via backticks inherits project lib dir ($lib_dir) via PERL5LIB"
+) or diag "Child \@INC was: @child_inc";
+
+done_testing;
diff --git a/t/integration/includes/default-i.tx b/t/integration/includes/default-i.tx
index f5c90d447..d77d38f01 100644
--- a/t/integration/includes/default-i.tx
+++ b/t/integration/includes/default-i.tx
@@ -1,6 +1,7 @@
 use Test2::V0;
 
 use File::Spec;
+use Config qw/%Config/;
 
 my @parts = File::Spec->splitpath(File::Spec->rel2abs(__FILE__));
 pop @parts;
@@ -20,6 +21,16 @@ like(
     "Added lib, blib/lib, and blib/arch AFTER the -Ixyz"
 );
 
-is($ENV{PERL5LIB}, $ENV{OLD_PERL5LIB}, "PERL5LIB has not been modified");
+like(
+    [split $Config{path_sep}, $ENV{PERL5LIB}],
+    [
+        App::Yath->app_path,
+        File::Spec->catdir($path, 'xyz'),
+        File::Spec->catdir($path, 'lib'),
+        File::Spec->catdir($path, 'blib', 'lib'),
+        File::Spec->catdir($path, 'blib', 'arch'),
+    ],
+    "PERL5LIB includes all lib paths so child processes inherit them"
+);
 
 done_testing;
diff --git a/t/integration/includes/default.tx b/t/integration/includes/default.tx
index 163114a8a..7788f6dff 100644
--- a/t/integration/includes/default.tx
+++ b/t/integration/includes/default.tx
@@ -3,6 +3,7 @@ use Test2::V0;
 require App::Yath;
 
 use File::Spec;
+use Config qw/%Config/;
 
 my @parts = File::Spec->splitpath(File::Spec->rel2abs(__FILE__));
 pop @parts;
@@ -19,6 +20,15 @@ like(
     "Added lib, blib/lib, and blib/arch to the front of the line"
 );
 
-is($ENV{PERL5LIB}, $ENV{OLD_PERL5LIB}, "PERL5LIB has not been modified");
+like(
+    [split $Config{path_sep}, $ENV{PERL5LIB}],
+    [
+        App::Yath->app_path,
+        File::Spec->catdir($path, 'lib'),
+        File::Spec->catdir($path, 'blib', 'lib'),
+        File::Spec->catdir($path, 'blib', 'arch'),
+    ],
+    "PERL5LIB includes lib paths so child processes inherit them"
+);
 
 done_testing;
diff --git a/t/integration/includes/dot-last.tx b/t/integration/includes/dot-last.tx
index b048c5763..b924b8f58 100644
--- a/t/integration/includes/dot-last.tx
+++ b/t/integration/includes/dot-last.tx
@@ -22,6 +22,6 @@ like(
 
 is($INC[-1], '.', "Dot added last");
 
-is($ENV{PERL5LIB}, $ENV{OLD_PERL5LIB}, "PERL5LIB has not been modified");
+isnt($ENV{PERL5LIB}, $ENV{OLD_PERL5LIB}, "PERL5LIB includes project lib paths for child process inheritance");
 
 done_testing;
diff --git a/t/integration/includes/order-ibili.tx b/t/integration/includes/order-ibili.tx
index 466101688..f40e90477 100644
--- a/t/integration/includes/order-ibili.tx
+++ b/t/integration/includes/order-ibili.tx
@@ -27,6 +27,6 @@ like(
     "Added all via cli, in order"
 );
 
-is($ENV{PERL5LIB}, $ENV{OLD_PERL5LIB}, "PERL5LIB has not been modified");
+isnt($ENV{PERL5LIB}, $ENV{OLD_PERL5LIB}, "PERL5LIB includes project lib paths for child process inheritance");
 
 done_testing;
diff --git a/t/integration/includes/order-ilibi.tx b/t/integration/includes/order-ilibi.tx
index 6abd157f9..1be9c0fe5 100644
--- a/t/integration/includes/order-ilibi.tx
+++ b/t/integration/includes/order-ilibi.tx
@@ -27,6 +27,6 @@ like(
     "Added all via cli, in order"
 );
 
-is($ENV{PERL5LIB}, $ENV{OLD_PERL5LIB}, "PERL5LIB has not been modified");
+isnt($ENV{PERL5LIB}, $ENV{OLD_PERL5LIB}, "PERL5LIB includes project lib paths for child process inheritance");
 
 done_testing;