diff --git a/tests/reftests/dune.inc b/tests/reftests/dune.inc
index e9190d12e7d..807f14b3cda 100644
--- a/tests/reftests/dune.inc
+++ b/tests/reftests/dune.inc
@@ -1538,7 +1538,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-N0REP0})))))
 
 (rule
@@ -1559,7 +1559,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-0070613707})))))
 
 (rule
@@ -1580,7 +1580,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-009e00fa})))))
 
 (rule
@@ -1601,7 +1601,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-11ea1cb})))))
 
 (rule
@@ -1622,7 +1622,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-297366c})))))
 
 (rule
@@ -1643,7 +1643,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-3235916})))))
 
 (rule
@@ -1664,7 +1664,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-7090735c})))))
 
 (rule
@@ -1685,7 +1685,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-7371c1d9})))))
 
 (rule
@@ -1706,7 +1706,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-a5d7cdc0})))))
 
 (rule
@@ -1727,7 +1727,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-ad4dd344})))))
 
 (rule
@@ -1748,7 +1748,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-c1842d168d})))))
 
 (rule
@@ -1769,7 +1769,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-c1ba97dafe95c865d37ad4d88f6e57c9ffbe7f0a})))))
 
 (rule
@@ -1790,7 +1790,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-c1d23f0e})))))
 
 (rule
@@ -1811,7 +1811,7 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-de897adf36c4230dfea812f40c98223b31c4521a})))))
 
 (rule
@@ -1832,5 +1832,5 @@
    (progn
     (ignore-stdout
     (run %{bin:opam} init --root=%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%{dep:opam-repo-f372039d})))))
diff --git a/tests/reftests/gen.ml b/tests/reftests/gen.ml
index cee668ae52e..15a2815ace8 100644
--- a/tests/reftests/gen.ml
+++ b/tests/reftests/gen.ml
@@ -80,7 +80,7 @@ let opam_init_rule archive_hash =
    (progn
     (ignore-stdout
     (run %%{bin:opam} init --root=%%{targets}
-           --no-setup --bypass-checks --no-opamrc --bare
+           --no-setup --no-cygwin-setup --bypass-checks --no-opamrc --bare
            file://%%{dep:%s})))))
 |} (opamroot_directory ~archive_hash) (repo_directory ~archive_hash)