diff --git a/samples/zephyr/Makefile b/samples/zephyr/Makefile
index 62291e3..ab5c975 100644
--- a/samples/zephyr/Makefile
+++ b/samples/zephyr/Makefile
@@ -106,10 +106,10 @@
 	(mkdir -p $(BUILD_DIR_BOOT) && \
 		cd $(BUILD_DIR_BOOT) && \
 		cmake -DOVERLAY_CONFIG=$(BOOTLOADER_OVERLAY_CONFIG) \
-			-G"Unix Makefiles" \
+			-G"Ninja" \
 			-DBOARD=$(BOARD) \
 			$(SOURCE_DIRECTORY)/../../boot/zephyr && \
-		make -j$(nproc))
+		ninja)
 	cp $(BUILD_DIR_BOOT)/zephyr/zephyr.bin mcuboot.bin
 
 clean_boot: check
@@ -120,10 +120,10 @@
 	(mkdir -p $(BUILD_DIR_HELLO1) && \
 		cd $(BUILD_DIR_HELLO1) && \
 		cmake -DFROM_WHO=hello1 \
-			-G"Unix Makefiles" \
+			-G"Ninja" \
 			-DBOARD=$(BOARD) \
 			$(SOURCE_DIRECTORY)/hello-world && \
-		make -j$(nproc))
+		ninja)
 	$(IMGTOOL) sign \
 		--key $(SIGNING_KEY) \
 		--header-size $(BOOT_HEADER_LEN) \
@@ -145,10 +145,10 @@
 	(mkdir -p $(BUILD_DIR_HELLO2) && \
 		cd $(BUILD_DIR_HELLO2) && \
 		cmake -DFROM_WHO=hello2 \
-			-G"Unix Makefiles" \
+			-G"Ninja" \
 			-DBOARD=$(BOARD) \
 			$(SOURCE_DIRECTORY)/hello-world && \
-		make -j$(nproc))
+		ninja)
 	$(IMGTOOL) sign \
 		--key $(SIGNING_KEY) \
 		--header-size $(BOOT_HEADER_LEN) \
diff --git a/samples/zephyr/README.md b/samples/zephyr/README.md
index cd99247..b19a0a9 100644
--- a/samples/zephyr/README.md
+++ b/samples/zephyr/README.md
@@ -8,3 +8,17 @@
 
 Please see the comments in the Makefile in this directory for more
 details on how to build and test this application.
+
+Note that this sample uses the "ninja" build tool, which can be
+installed on most systems using the system package manager, e.g., for
+a Debian-based distro:
+
+```
+$ sudo apt-get install ninja
+```
+
+or in Fedora:
+
+```
+$ sudo dnf install ninja
+```