diff --git a/pkg/fpgacontroller/patcher/patcher.go b/pkg/fpgacontroller/patcher/patcher.go
index ba1d0f51..bbee9254 100644
--- a/pkg/fpgacontroller/patcher/patcher.go
+++ b/pkg/fpgacontroller/patcher/patcher.go
@@ -133,14 +133,17 @@ func (p *patcher) RemoveRegion(name string) {
 	delete(p.resourceModeMap, namespace+"/"+name)
 }
 
-// getRequestedResources validates the container's requirements first, then returns them as a map.
-func getRequestedResources(container corev1.Container) (map[string]int64, error) {
+func validateContainer(container corev1.Container) error {
 	for _, v := range container.Env {
 		if strings.HasPrefix(v.Name, "FPGA_REGION") || strings.HasPrefix(v.Name, "FPGA_AFU") {
-			return nil, errors.Errorf("environment variable '%s' is not allowed", v.Name)
+			return errors.Errorf("environment variable '%s' is not allowed", v.Name)
 		}
 	}
+	return nil
+}
 
+// getRequestedResources validates the container's requirements first, then returns them as a map.
+func getRequestedResources(container corev1.Container) (map[string]int64, error) {
 	// Container may happen to have Requests, but not Limits. Check Requests first,
 	// then in the next loop iterate over Limits.
 	for resourceName, resourceQuantity := range container.Resources.Requests {
@@ -183,6 +186,10 @@ func getRequestedResources(container corev1.Container) (map[string]int64, error)
 }
 
 func (p *patcher) getPatchOps(containerIdx int, container corev1.Container) ([]string, error) {
+	if err := validateContainer(container); err != nil {
+		return nil, err
+	}
+
 	requestedResources, err := getRequestedResources(container)
 	if err != nil {
 		return nil, err
@@ -203,14 +210,11 @@ func (p *patcher) getPatchOps(containerIdx int, container corev1.Container) ([]s
 		}
 
 		switch mode {
-		case regiondevel:
+		case regiondevel, af:
 			// Do nothing.
-			// The requested resources are exposed by FPGA plugins working in "regiondevel" mode.
-			// In this mode the workload is supposed to program FPGA regions.
+			// The requested resources are exposed by FPGA plugins working in "regiondevel/af" mode.
+			// In "regiondevel" mode the workload is supposed to program FPGA regions.
 			// A cluster admin has to add FpgaRegion CRDs to allow this.
-		case af:
-			// Do nothing.
-			// The requested resources are exposed by FPGA plugins working in "af" mode.
 		case region:
 			// Let fpga_crihook know how to program the regions by setting ENV variables.
 			// The requested resources are exposed by FPGA plugins working in "region" mode.
diff --git a/pkg/fpgacontroller/patcher/patcher_test.go b/pkg/fpgacontroller/patcher/patcher_test.go
index 41b96c5a..bbc1c725 100644
--- a/pkg/fpgacontroller/patcher/patcher_test.go
+++ b/pkg/fpgacontroller/patcher/patcher_test.go
@@ -86,6 +86,71 @@ func TestPatcherStorageFunctions(t *testing.T) {
 	}
 }
 
+func TestValidateContainerEnv(t *testing.T) {
+	tcases := []struct {
+		name        string
+		container   corev1.Container
+		expectedErr bool
+	}{
+		{
+			name: "Container OK",
+			container: corev1.Container{
+				Resources: corev1.ResourceRequirements{
+					Limits: corev1.ResourceList{
+						"cpu": resource.MustParse("1"),
+					},
+				},
+			},
+			expectedErr: false,
+		},
+		{
+			name: "Wrong ENV FPGA_AFU",
+			container: corev1.Container{
+				Resources: corev1.ResourceRequirements{
+					Limits: corev1.ResourceList{
+						"cpu": resource.MustParse("1"),
+					},
+				},
+				Env: []corev1.EnvVar{
+					{
+						Name:  "FPGA_AFU",
+						Value: "fake value",
+					},
+				},
+			},
+			expectedErr: true,
+		},
+		{
+			name: "Wrong ENV FPGA_REGION",
+			container: corev1.Container{
+				Resources: corev1.ResourceRequirements{
+					Limits: corev1.ResourceList{
+						"cpu": resource.MustParse("1"),
+					},
+				},
+				Env: []corev1.EnvVar{
+					{
+						Name:  "FPGA_REGION",
+						Value: "fake value",
+					},
+				},
+			},
+			expectedErr: true,
+		},
+	}
+	for _, tt := range tcases {
+		t.Run(tt.name, func(t *testing.T) {
+			err := validateContainer(tt.container)
+			if tt.expectedErr && err == nil {
+				t.Errorf("Test case '%s': no error returned", tt.name)
+			}
+			if !tt.expectedErr && err != nil {
+				t.Errorf("Test case '%s': unexpected error: %+v", tt.name, err)
+			}
+		})
+	}
+}
+
 func TestGetPatchOps(t *testing.T) {
 	tcases := []struct {
 		name        string
@@ -229,23 +294,6 @@ func TestGetPatchOps(t *testing.T) {
 			},
 			expectedErr: true,
 		},
-		{
-			name: "Wrong ENV",
-			container: corev1.Container{
-				Resources: corev1.ResourceRequirements{
-					Limits: corev1.ResourceList{
-						"cpu": resource.MustParse("1"),
-					},
-				},
-				Env: []corev1.EnvVar{
-					{
-						Name:  "FPGA_REGION",
-						Value: "fake value",
-					},
-				},
-			},
-			expectedErr: true,
-		},
 		{
 			name: "Wrong type of quantity",
 			container: corev1.Container{