diff --git a/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirCodeSystemLookupController.java b/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirCodeSystemLookupController.java
index 2be5784cc1..9acd47cb6c 100644
--- a/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirCodeSystemLookupController.java
+++ b/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirCodeSystemLookupController.java
@@ -239,8 +239,11 @@ public Promise<ResponseEntity<byte[]>> lookup(
 		@RequestHeader(value = HttpHeaders.ACCEPT)
 		final String accept,
 		
-		@Parameter(description = "Prefer header", schema = @Schema(allowableValues = {"strict", "lenient"}, defaultValue = "lenient"))
-		@RequestHeader(value = "Prefer", required = false)
+		@Parameter(description = "Prefer header", schema = @Schema(
+			allowableValues = { PREFER_HANDLING_STRICT, PREFER_HANDLING_LENIENT }, 
+			defaultValue = PREFER_HANDLING_LENIENT
+		))
+		@RequestHeader(value = PREFER, required = false)
 		final String prefer,
 
 		@Parameter(description = "Alternative response format", schema = @Schema(allowableValues = {
diff --git a/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirCodeSystemSubsumesController.java b/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirCodeSystemSubsumesController.java
index fbb30b56bc..bc56187ec1 100644
--- a/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirCodeSystemSubsumesController.java
+++ b/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirCodeSystemSubsumesController.java
@@ -301,8 +301,11 @@ public Promise<ResponseEntity<byte[]>> subsumes(
 		@RequestHeader(value = HttpHeaders.ACCEPT)
 		final String accept,
 		
-		@Parameter(description = "Prefer header", schema = @Schema(allowableValues = {"strict", "lenient"}, defaultValue = "lenient"))
-		@RequestHeader(value = "Prefer", required = false)
+		@Parameter(description = "Prefer header", schema = @Schema(
+			allowableValues = { PREFER_HANDLING_STRICT, PREFER_HANDLING_LENIENT }, 
+			defaultValue = PREFER_HANDLING_LENIENT
+		))
+		@RequestHeader(value = PREFER, required = false)
 		final String prefer,
 
 		@Parameter(description = "Alternative response format", schema = @Schema(allowableValues = {
@@ -418,8 +421,11 @@ public Promise<ResponseEntity<byte[]>> subsumes(
 		@RequestHeader(value = HttpHeaders.ACCEPT)
 		final String accept,
 		
-		@Parameter(description = "Prefer header", schema = @Schema(allowableValues = {"strict", "lenient"}, defaultValue = "lenient"))
-		@RequestHeader(value = "Prefer", required = false)
+		@Parameter(description = "Prefer header", schema = @Schema(
+			allowableValues = { PREFER_HANDLING_STRICT, PREFER_HANDLING_LENIENT }, 
+			defaultValue = PREFER_HANDLING_LENIENT
+		))
+		@RequestHeader(value = PREFER, required = false)
 		final String prefer,
 
 		@Parameter(description = "Alternative response format", schema = @Schema(allowableValues = {
diff --git a/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirCodeSystemValidateCodeController.java b/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirCodeSystemValidateCodeController.java
index 430033fc96..f05c06e0e9 100644
--- a/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirCodeSystemValidateCodeController.java
+++ b/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirCodeSystemValidateCodeController.java
@@ -237,8 +237,11 @@ public Promise<ResponseEntity<byte[]>> validateCode(
 		@RequestHeader(value = HttpHeaders.ACCEPT)
 		final String accept,
 		
-		@Parameter(description = "Prefer header", schema = @Schema(allowableValues = {"strict", "lenient"}, defaultValue = "lenient"))
-		@RequestHeader(value = "Prefer", required = false)
+		@Parameter(description = "Prefer header", schema = @Schema(
+			allowableValues = { PREFER_HANDLING_STRICT, PREFER_HANDLING_LENIENT }, 
+			defaultValue = PREFER_HANDLING_LENIENT
+		))
+		@RequestHeader(value = PREFER, required = false)
 		final String prefer,
 
 		@Parameter(description = "Alternative response format", schema = @Schema(allowableValues = {
@@ -470,8 +473,11 @@ public Promise<ResponseEntity<byte[]>> validateCode(
 		@RequestHeader(value = HttpHeaders.ACCEPT)
 		final String accept,
 		
-		@Parameter(description = "Prefer header", schema = @Schema(allowableValues = {"strict", "lenient"}, defaultValue = "lenient"))
-		@RequestHeader(value = "Prefer", required = false)
+		@Parameter(description = "Prefer header", schema = @Schema(
+			allowableValues = { PREFER_HANDLING_STRICT, PREFER_HANDLING_LENIENT }, 
+			defaultValue = PREFER_HANDLING_LENIENT
+		))
+		@RequestHeader(value = PREFER, required = false)
 		final String prefer,
 
 		@Parameter(description = "Alternative response format", schema = @Schema(allowableValues = {
diff --git a/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirConceptMapTranslateController.java b/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirConceptMapTranslateController.java
index 986073f1e9..7e45158ae1 100644
--- a/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirConceptMapTranslateController.java
+++ b/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirConceptMapTranslateController.java
@@ -237,8 +237,11 @@ public Promise<ResponseEntity<byte[]>> translate(
 		@RequestHeader(value = HttpHeaders.ACCEPT)
 		final String accept,
 		
-		@Parameter(description = "Prefer header", schema = @Schema(allowableValues = {"strict", "lenient"}, defaultValue = "lenient"))
-		@RequestHeader(value = "Prefer", required = false)
+		@Parameter(description = "Prefer header", schema = @Schema(
+			allowableValues = { PREFER_HANDLING_STRICT, PREFER_HANDLING_LENIENT }, 
+			defaultValue = PREFER_HANDLING_LENIENT
+		))
+		@RequestHeader(value = PREFER, required = false)
 		final String prefer,
 
 		@Parameter(description = "Alternative response format", schema = @Schema(allowableValues = {
@@ -471,8 +474,11 @@ public Promise<ResponseEntity<byte[]>> translate(
 		@RequestHeader(value = HttpHeaders.ACCEPT)
 		final String accept,
 		
-		@Parameter(description = "Prefer header", schema = @Schema(allowableValues = {"strict", "lenient"}, defaultValue = "lenient"))
-		@RequestHeader(value = "Prefer", required = false)
+		@Parameter(description = "Prefer header", schema = @Schema(
+			allowableValues = { PREFER_HANDLING_STRICT, PREFER_HANDLING_LENIENT }, 
+			defaultValue = PREFER_HANDLING_LENIENT
+		))
+		@RequestHeader(value = PREFER, required = false)
 		final String prefer,
 
 		@Parameter(description = "Alternative response format", schema = @Schema(allowableValues = {
diff --git a/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirValueSetExpandOperationController.java b/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirValueSetExpandOperationController.java
index 0369a0a409..79f77f7509 100644
--- a/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirValueSetExpandOperationController.java
+++ b/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirValueSetExpandOperationController.java
@@ -254,8 +254,11 @@ public Promise<ResponseEntity<byte[]>> expand(
 		@RequestHeader(value = HttpHeaders.ACCEPT)
 		final String accept,
 		
-		@Parameter(description = "Prefer header", schema = @Schema(allowableValues = {"strict", "lenient"}, defaultValue = "lenient"))
-		@RequestHeader(value = "Prefer", required = false)
+		@Parameter(description = "Prefer header", schema = @Schema(
+			allowableValues = { PREFER_HANDLING_STRICT, PREFER_HANDLING_LENIENT }, 
+			defaultValue = PREFER_HANDLING_LENIENT
+		))
+		@RequestHeader(value = PREFER, required = false)
 		final String prefer,
 
 		@Parameter(description = "Alternative response format", schema = @Schema(allowableValues = {
diff --git a/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirValueSetValidateCodeController.java b/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirValueSetValidateCodeController.java
index 4d19eec4eb..fbdacd898c 100644
--- a/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirValueSetValidateCodeController.java
+++ b/fhir/com.b2international.snowowl.fhir.rest/src/com/b2international/snowowl/fhir/rest/FhirValueSetValidateCodeController.java
@@ -249,8 +249,11 @@ public Promise<ResponseEntity<byte[]>> validateCode(
 		@RequestHeader(value = HttpHeaders.ACCEPT)
 		final String accept,
 		
-		@Parameter(description = "Prefer header", schema = @Schema(allowableValues = {"strict", "lenient"}, defaultValue = "lenient"))
-		@RequestHeader(value = "Prefer", required = false)
+		@Parameter(description = "Prefer header", schema = @Schema(
+			allowableValues = { PREFER_HANDLING_STRICT, PREFER_HANDLING_LENIENT }, 
+			defaultValue = PREFER_HANDLING_LENIENT
+		))
+		@RequestHeader(value = PREFER, required = false)
 		final String prefer,
 
 		@Parameter(description = "Alternative response format", schema = @Schema(allowableValues = {
@@ -495,8 +498,11 @@ public Promise<ResponseEntity<byte[]>> validateCode(
 		@RequestHeader(value = HttpHeaders.ACCEPT)
 		final String accept,
 
-		@Parameter(description = "Prefer header", schema = @Schema(allowableValues = {"strict", "lenient"}, defaultValue = "lenient"))
-		@RequestHeader(value = "Prefer", required = false)
+		@Parameter(description = "Prefer header", schema = @Schema(
+			allowableValues = { PREFER_HANDLING_STRICT, PREFER_HANDLING_LENIENT }, 
+			defaultValue = PREFER_HANDLING_LENIENT
+		))
+		@RequestHeader(value = PREFER, required = false)
 		final String prefer,
 		
 		@Parameter(description = "Alternative response format", schema = @Schema(allowableValues = {