diff --git a/src/crypto/x509/root_cgo_darwin.go b/src/crypto/x509/root_cgo_darwin.go
index 255a8d3525..a467255a54 100644
--- a/src/crypto/x509/root_cgo_darwin.go
+++ b/src/crypto/x509/root_cgo_darwin.go
@@ -280,6 +280,8 @@ int CopyPEMRoots(CFDataRef *pemRoots, CFDataRef *untrustedPemRoots, bool debugDa
 import "C"
 import (
 	"errors"
+	"io/ioutil"
+	"os"
 	"unsafe"
 )
 
@@ -295,6 +297,13 @@ func loadSystemRoots() (*CertPool, error) {
 	buf := C.GoBytes(unsafe.Pointer(C.CFDataGetBytePtr(data)), C.int(C.CFDataGetLength(data)))
 	roots := NewCertPool()
 	roots.AppendCertsFromPEM(buf)
+	if file := os.Getenv("NIX_SSL_CERT_FILE"); file != "" {
+		data, err := ioutil.ReadFile(file)
+		if err == nil {
+			roots.AppendCertsFromPEM(data)
+			return roots, nil
+		}
+	}
 
 	if C.CFDataGetLength(untrustedData) == 0 {
 		return roots, nil
diff --git a/src/crypto/x509/root_darwin.go b/src/crypto/x509/root_darwin.go
index 2f6a8b8d60..b81889fe69 100644
--- a/src/crypto/x509/root_darwin.go
+++ b/src/crypto/x509/root_darwin.go
@@ -92,6 +92,14 @@ func execSecurityRoots() (*CertPool, error) {
 		verifyCh    = make(chan rootCandidate)
 	)
 
+	if file := os.Getenv("NIX_SSL_CERT_FILE"); file != "" {
+		data, err := ioutil.ReadFile(file)
+		if err == nil {
+			roots.AppendCertsFromPEM(data)
+			return roots, nil
+		}
+	}
+
 	// Using 4 goroutines to pipe into verify-cert seems to be
 	// about the best we can do. The verify-cert binary seems to
 	// just RPC to another server with coarse locking anyway, so
diff --git a/src/crypto/x509/root_unix.go b/src/crypto/x509/root_unix.go
index 48de50b4ea..750e12c6b4 100644
--- a/src/crypto/x509/root_unix.go
+++ b/src/crypto/x509/root_unix.go
@@ -38,6 +38,13 @@ func (c *Certificate) systemVerify(opts *VerifyOptions) (chains [][]*Certificate
 
 func loadSystemRoots() (*CertPool, error) {
 	roots := NewCertPool()
+	if file := os.Getenv("NIX_SSL_CERT_FILE"); file != "" {
+		data, err := ioutil.ReadFile(file)
+		if err == nil {
+			roots.AppendCertsFromPEM(data)
+			return roots, nil
+		}
+	}
 
 	files := certFiles
 	if f := os.Getenv(certFileEnv); f != "" {