diff --git a/include/kernaux/pfa.h b/include/kernaux/pfa.h
index 2a63f6d..d91863f 100644
--- a/include/kernaux/pfa.h
+++ b/include/kernaux/pfa.h
@@ -24,6 +24,13 @@ void KernAux_PFA_mark_available(
 )
 __attribute__((nonnull));
 
+void KernAux_PFA_mark_unavailable(
+    struct KernAux_PFA *pfa,
+    unsigned int start,
+    unsigned int end
+)
+__attribute__((nonnull));
+
 unsigned int KernAux_PFA_alloc_page(struct KernAux_PFA *pfa)
 __attribute__((nonnull));
 
diff --git a/src/pfa.c b/src/pfa.c
index 360a1da..78aade2 100644
--- a/src/pfa.c
+++ b/src/pfa.c
@@ -3,6 +3,14 @@
 #include <kernaux/pfa.h>
 #include <kernaux/stdlib.h>
 
+static void KernAux_PFA_mark(
+    struct KernAux_PFA *pfa,
+    kernaux_bool status,
+    unsigned int start,
+    unsigned int end
+)
+__attribute__((nonnull));
+
 void KernAux_PFA_initialize(struct KernAux_PFA *const pfa)
 {
     kernaux_memset(pfa->pages, KERNAUX_FALSE, sizeof(pfa->pages));
@@ -12,6 +20,23 @@ void KernAux_PFA_mark_available(
     struct KernAux_PFA *const pfa,
     unsigned int start,
     unsigned int end
+) {
+    KernAux_PFA_mark(pfa, KERNAUX_TRUE, start, end);
+}
+
+void KernAux_PFA_mark_unavailable(
+    struct KernAux_PFA *const pfa,
+    unsigned int start,
+    unsigned int end
+) {
+    KernAux_PFA_mark(pfa, KERNAUX_FALSE, start, end);
+}
+
+void KernAux_PFA_mark(
+    struct KernAux_PFA *const pfa,
+    const kernaux_bool status,
+    unsigned int start,
+    unsigned int end
 ) {
     if (start >= end) {
         return;
@@ -32,7 +57,7 @@ void KernAux_PFA_mark_available(
     const unsigned int end_index   = end   / KERNAUX_PFA_PAGE_SIZE;
 
     for (unsigned int index = start_index; index <= end_index; ++index) {
-        pfa->pages[index] = KERNAUX_TRUE;
+        pfa->pages[index] = status;
     }
 }
 
diff --git a/tests/test_pfa.c b/tests/test_pfa.c
index 04ad6dd..da23316 100644
--- a/tests/test_pfa.c
+++ b/tests/test_pfa.c
@@ -14,6 +14,7 @@ int main()
 
     KernAux_PFA_mark_available(&pfa, 0, 654335);
     KernAux_PFA_mark_available(&pfa, 1048576, 134086655);
+    KernAux_PFA_mark_unavailable(&pfa, 4194304, 6291455); // [4 MB, 6 MB)
 
     for (unsigned int index = 0; index < 159; ++index) {
         assert(pfa.pages[index] == KERNAUX_TRUE);
@@ -23,7 +24,15 @@ int main()
         assert(pfa.pages[index] == KERNAUX_FALSE);
     }
 
-    for (unsigned int index = 256; index < 32736; ++index) {
+    for (unsigned int index = 256; index < 1024; ++index) { // [1 MB, 4 MB)
+        assert(pfa.pages[index] == KERNAUX_TRUE);
+    }
+
+    for (unsigned int index = 1024; index < 1536; ++index) { // [4 MB, 6 MB)
+        assert(pfa.pages[index] == KERNAUX_FALSE);
+    }
+
+    for (unsigned int index = 1536; index < 32736; ++index) { // [6 MB, ~127 MB)
         assert(pfa.pages[index] == KERNAUX_TRUE);
     }